Extended Reference Intra-Picture Prediction

ABSTRACT

A video encoder is configured to encode, by block based predictive encoding, pictures of a video into coding data, wherein the block based predictive encoding includes an intra-picture prediction. The video encoder is configured to use, for the intra-picture prediction, for encoding a prediction block of a picture, a plurality of nearest reference samples of the picture directly neighboring the prediction block and a plurality of extended reference samples, each extended reference sample of the plurality of extended reference samples separated from the prediction block at least by one nearest reference sample of the plurality of reference samples. The video encoder is further configured to sequentially determine an availability or unavailability of each of the plurality of nearest reference samples and to substitute a nearest reference sample being determined as unavailable by a substitution sample. The video encoder is configured to use the substitution sample for the intra-picture prediction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending InternationalApplication No. PCT/EP2019/067412, filed Jun. 28, 2019, which isincorporated herein by reference in its entirety, and additionallyclaims priority from European Application No. EP 18180960.9, filed Jun.29, 2018, which is also incorporated herein by reference in itsentirety.

The present invention relates to video coding, in particular hybridvideo coding comprising an intra-picture prediction. The presentinvention further relates to a video encoder, a video decoder andmethods for video encoding, decoding, respectively.

BACKGROUND OF THE INVENTION

H.265/HEVC is video codec which already provides tools for elevating oreven enabling parallel processing at encoder and/or decoder. Forinstance, HEVC supports a sub-division of pictures into an array oftiles which are encoded independently from each other. Another conceptsupported by HEVC pertains to WPP, according to which CTU rows orCTU-lines of the pictures may be processed in parallel from left toright, i.e. in stripes, provided that some minimum CTU offset is obeyedin the processing of consecutive CTU lines. It would be favorable,however, to have a video codec at hand which supports parallelprocessing capabilities of video encoders and/or video decoders evenmore efficiently.

SUMMARY

An embodiment may have a video decoder configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; use, in the intra-picture prediction, for encoding aprediction block of a picture, a plurality of extended reference samplesof the picture, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples,directly neighboring the prediction block; sequentially determine anavailability or unavailability of each of the plurality of extendedreference samples; substitute an extended reference sample beingdetermined as unavailable by a substitution sample; and use thesubstitution sample for the intra-picture prediction.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction. The video encoder is configured to use, for theintra-picture prediction, for encoding a prediction block of a picture,a plurality of extended reference samples of the picture, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples, directly neighboring theprediction block. The video encoder is further configured tosequentially determine an availability or unavailability of each of theplurality of nearest reference samples and to substitute a nearestreference sample being determined as unavailable by a substitutionsample. The video encoder is configured to use the substitution samplefor the intra-picture prediction. This allows to use prediction conceptsusing nearest reference samples even if such samples are unavailablewhich may occur, for example, when having a line or row of samples in abuffer/memory whilst not actually having a column of samples in thememory being thus unavailable.

According to an embodiment a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction. The video encoder is configured to use, in the intra-pictureprediction, for encoding a prediction block of a picture, a plurality ofextended reference samples of the picture, each extended referencesample of the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples, directly neighboring the predictionblock. The video encoder is further configured to filter at least asubset of the plurality of extended reference samples using a bilateralfilter so as to obtain a plurality of filtered extended referencesamples; and to use the plurality of filtered extended reference samplesfor the intra-picture prediction.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction. The video encoder is configured to use, in the intra-pictureprediction, for encoding a prediction block of a picture, a plurality ofextended reference samples of the picture, each extended referencesample of the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples, directly neighboring the predictionblock, wherein a plurality of nearest reference samples is arrangedalong a first picture direction of the prediction block and along asecond picture direction of the prediction block; and to map at least apart of the nearest reference samples arranged along the seconddirection to extended reference samples being arranged along the firstdirection, such that the mapped reference samples exceed an extension ofthe prediction block along the first picture direction. The videoencoder is configured to use the mapped extended reference samples forthe prediction.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction. The video encoder is configured to use, for theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and a plurality of extended referencesamples, each extended reference sample of the plurality of extendedreference samples separated from the prediction block at least by onenearest reference sample of the plurality of reference samples, whereinthe video encoder is configured to boundary filtering in a mode where noextended samples are used; and not to use boundary filtering whenextended samples are used; or wherein the video encoder is configured toboundary filtering at least a subset of the plurality of nearestreference samples and not using boundary filtering for the extendedsamples.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction. The video encoder is configured to determine, in theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and a plurality of extended referencesamples, each extended reference sample of the plurality of extendedreference samples separated from the prediction block at least by onenearest reference sample of the plurality of reference samples. Thevideo encoder is further configured to determine a prediction for theprediction block using the extended reference samples and to filter theextended reference samples so as to obtain a plurality of filteredextended reference samples; and to combine the prediction and thefiltered extended reference samples so as to obtain a combinedprediction for the prediction block.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction. The video encoder is configured to use, for theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and/or a plurality of extendedreference samples, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples;to determine a first prediction for the prediction block using a firstprediction mode of a set of prediction modes, the first set ofprediction modes comprising prediction modes using the plurality ofnearest reference samples in absence of the extended reference samples;and to determine a second prediction for the prediction block using asecond prediction mode of a second set of prediction modes, the secondset of prediction modes comprising a subset of the prediction modes ofthe first set, the subset being associated with the plurality ofextended reference samples. The video encoder is configured toweightedly (w₀; w_(i)) combine the first prediction (p₀(x,y)) and thesecond prediction (p₀(x,y)) so as to obtain a combined prediction(p(x,y)) as prediction for the prediction block in the coding data.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for encoding aprediction block of a picture, a plurality of nearest reference samplesof the picture directly neighboring the prediction block and/or aplurality of extended reference samples, each extended reference sampleof the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples; to use a prediction mode being one of afirst set of prediction modes for predicting the prediction block usingthe nearest reference samples, e.g., in absence of extended referencesamples; or being one of a second set of prediction modes for predictingthe prediction block using the extended reference samples; wherein thesecond set of prediction modes is a subset of the first set ofprediction modes; to signal a mode information (m) indicating theprediction mode used for predicting the prediction block; and toafterwards signal a parameter information (i) indicating a subset of theextended reference samples used for the prediction mode if theprediction mode is contained in the second set of prediction modes; andto skip signaling the parameter information when the used predictionmode is not contained in the second set of prediction modes, therebyallowing a conclusion at the decoder that a specific value of theparameter is chosen or selected ort determined, the predefined natureallowing skipping of the signaling, i.e., the absence of the signal isgiven an informative meaning. For example, the absence may indicate thatthe nearest reference samples have to be used.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for encoding aprediction block of a picture, a plurality of reference samplescomprising nearest reference samples of the picture directly neighboringthe prediction block and a plurality of extended reference samples, eachextended reference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples; to use a prediction modebeing one of a first set of prediction modes for predicting theprediction block using the nearest reference samples; or being one of asecond set of prediction modes for predicting the prediction block usingthe extended reference samples; wherein the second set of predictionmodes is a subset of the first set of prediction modes. The videoencoder may use available reference data so as to generate the first setand/or the second set and/or may determine the set using informationderived from the pictures. The second set being a subset of the firstset includes the case that both sets are equal. The video encoder isconfigured to signal a parameter information indicating a subset of theplurality of reference samples used for the prediction mode, the subsetof the plurality of reference samples comprising nearest referencesamples only or extended reference samples; and to afterwards signal amode information (m) indicating the prediction mode used for predictingthe prediction block, wherein the mode information indicates aprediction mode from a subset of modes, the subset being restricted to aset of allowed prediction modes according to the parameter information(i). Based on an association of the references samples used, i.e.,nearest or extended, an identification of the restricted set is possibleas only those prediction modes apply which are associated with thereference samples indicated.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for encoding aprediction block of a picture, a plurality of nearest reference samplesof the picture directly neighboring the prediction block and/or aplurality of extended reference samples, each extended reference sampleof the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples; to determine a first prediction for theprediction block using a first prediction mode of a set of predictionmodes, the first set of prediction modes comprising prediction modesusing the plurality of nearest reference samples in absence of theextended reference samples; and to determine a second prediction for theprediction block using a second prediction mode of a second set ofprediction modes, the second set of prediction modes comprising a subsetof the prediction modes of the first set being associated with theplurality of extended reference samples. The video encoder is configuredto combine the first prediction and the second prediction so as toobtain a combined prediction as prediction for the prediction block inthe coding data.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding, pictures of a video into coding data,wherein the block based predictive encoding comprises an intra-pictureprediction; to use, in the intra-picture prediction, for encoding aprediction block of a picture, a plurality of extended reference samplesof the picture, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples,directly neighboring the prediction block; and to use the plurality ofextended reference samples according to a predefined set of pluralitiesof extended reference samples. The pluralities of extended referencesamples, may be included, for example, in a list of area indices beingidentified by an identifier.

According to an embodiment, a video encoder is configured to encode, byblock based predictive encoding a plurality of prediction blocks,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, for theintra-picture prediction, for encoding a prediction block of theplurality of prediction blocks, a plurality of extended referencesamples of the picture, each extended reference sample of the pluralityof extended reference samples separated from the prediction block atleast by one nearest reference sample of the plurality of referencesamples, directly neighboring the prediction block. The video encoder isconfigured to determine the extended reference samples so as to be atleast partially a part of an adjacent prediction block of the pluralityof prediction blocks, and to determine that the adjacent predictionblock has not yet been predicted; and to signal information indicatingthe extended prediction samples associated to the prediction block andarranged in the adjacent prediction block as unavailable samples.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, in the intra-picture prediction, forencoding a prediction block of a picture, a plurality of extendedreference samples of the picture, each extended reference sample of theplurality of extended reference samples separated from the predictionblock at least by one nearest reference sample of the plurality ofreference samples, directly neighboring the prediction block; tosequentially determine an availability or unavailability of each of theplurality of nearest reference samples; to substitute a nearestreference sample being determined as unavailable by a substitutionsample; and to use the substitution sample for the intra-pictureprediction.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, in the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of extendedreference samples of the picture, each extended reference sample of theplurality of extended reference samples separated from the predictionblock at least by one nearest reference sample of the plurality ofreference samples, directly neighboring the prediction block; to filterat least a subset of the plurality of extended reference samples using abilateral filter so as to obtain a plurality of filtered extendedreference samples; and to use the plurality of filtered extendedreference samples for the intra-picture prediction.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, in the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of extendedreference samples of the picture, each extended reference sample of theplurality of extended reference samples separated from the predictionblock at least by one nearest reference sample of the plurality ofreference samples, directly neighboring the prediction block, wherein aplurality of nearest reference samples is arranged along a first picturedirection of the prediction block and along a second picture directionof the prediction block; to map at least a part of the nearest referencesamples arranged along the second direction to extended referencesamples being arranged along the first direction, such that the mappedreference samples exceed an extension of the prediction block along thefirst picture direction; and to use the mapped extended referencesamples for the prediction.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, for the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of nearestreference samples of the picture directly neighboring the predictionblock and a plurality of extended reference samples, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples. The video decoder isconfigured to boundary filtering in a mode where no extended samples areused; and not to use boundary filtering when extended samples are used;or to boundary filtering at least a subset of the plurality of nearestreference samples and not using boundary filtering for the extendedsamples.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to determine, in the intra-picture prediction,for decoding a prediction block of a picture, a plurality of nearestreference samples of the picture directly neighboring the predictionblock and a plurality of extended reference samples, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples; to determine a predictionfor the prediction block using the extended reference samples; to filterthe extended reference samples so as to obtain a plurality of filteredextended reference samples; and to combine the prediction and thefiltered extended reference samples so as to obtain a combinedprediction for the prediction block.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, for the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of nearestreference samples of the picture directly neighboring the predictionblock and/or a plurality of extended reference samples, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples; to determine a firstprediction for the prediction block using a first prediction mode of aset of prediction modes, the first set of prediction modes comprisingprediction modes using the plurality of nearest reference samples inabsence of the extended reference samples; and to determine a secondprediction for the prediction block using a second prediction mode of asecond set of prediction modes, the second set of prediction modescomprising a subset of the prediction modes of the first set, the subsetbeing associated with the plurality of extended reference samples. Thevideo decoder is configured to weightedly combine the first predictionand the second prediction so as to obtain a combined prediction asprediction for the prediction block in the coding data.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, for the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of nearestreference samples of the picture directly neighboring the predictionblock and/or a plurality of extended reference samples, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples; to use a prediction modebeing one of a first set of prediction modes for predicting theprediction block using the nearest reference samples; or being one of asecond set of prediction modes for predicting the prediction block usingthe extended reference samples; wherein the second set of predictionmodes is a subset of the first set of prediction modes; to receive amode information (m) indicating the prediction mode used for predictingthe prediction block; and to afterwards receive a parameter information(i) indicating a subset of the extended reference samples used for theprediction mode thereby indicating that the prediction mode is containedin the second set of prediction modes; and to determine that the usedprediction mode is not contained in the second set of prediction modeswhen not receiving the parameter information and to determine a use ofthe nearest reference samples for the prediction.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, for the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of referencesamples comprising nearest reference samples of the picture directlyneighboring the prediction block and a plurality of extended referencesamples, each extended reference sample of the plurality of extendedreference samples separated from the prediction block at least by onenearest reference sample of the plurality of reference samples; to use aprediction mode being one of a first set of prediction modes forpredicting the prediction block using the nearest reference samples; orbeing one of a second set of prediction modes for predicting theprediction block using the extended reference samples; wherein thesecond set of prediction modes is a subset of the first set ofprediction modes; to receive a parameter information (i) indicating asubset of the plurality of reference samples used for the predictionmode, the subset of the plurality of reference samples comprisingnearest reference samples only or at least one extended referencesample; and to afterwards receive a mode information (m) indicating theprediction mode used for predicting the prediction block; wherein themode information indicates a prediction mode from a subset of modes, thesubset being restricted to a set of allowed prediction modes accordingto the parameter information (i).

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; use, for the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of nearestreference samples of the picture directly neighboring the predictionblock and/or a plurality of extended reference samples, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples; to determine a firstprediction for the prediction block using a first prediction mode of aset of prediction modes, the first set of prediction modes comprisingprediction modes using the plurality of nearest reference samples inabsence of the extended reference samples; and to determine a secondprediction for the prediction block using a second prediction mode of asecond set of prediction modes, the second set of prediction modescomprising a subset of the prediction modes of the first set beingassociated with the plurality of extended reference samples. The videodecoder is configured to combine the first prediction and the secondprediction so as to obtain a combined prediction as prediction for theprediction block in the coding data.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, in the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of extendedreference samples of the picture, each extended reference sample of theplurality of extended reference samples separated from the predictionblock at least by one nearest reference sample of the plurality ofreference samples, directly neighboring the prediction block; and to usethe plurality of extended reference samples according to a predefinedset of pluralities of extended reference samples.

According to an embodiment, a video decoder is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein for each picture a plurality of prediction blocks isdecoded, wherein the block based predictive decoding comprises anintra-picture prediction; and to use, for the intra-picture prediction,for decoding a prediction block of the plurality of prediction blocks, aplurality of extended reference samples of the picture, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples, directly neighboring theprediction block. The video decoder is configured to determine theextended reference samples so as to be at least partially a part of anadjacent prediction block of the plurality of prediction blocks, and todetermine that the adjacent prediction block has not yet been predicted;and to receive information indicating the extended prediction samplesassociated to the prediction block and arranged in the adjacentprediction block as unavailable samples.

Further embodiments relate to methods for encoding and decoding a videoand to a computer program product.

With respect to the aforementioned embodiments of the presentapplication, it is noted that same may be combined so that more than oneof the aforementioned embodiments such as all embodiments areimplemented in a video codec concurrently.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 shows a schematic block diagram of a video encoder according toan embodiment, comprising a decoder according to an embodiment;

FIG. 2 shows a schematic flow chart of a method for encoding a videostream according to an embodiment;

FIG. 3 shows an example of directly neighboring (nearest) referencesamples and extended reference samples used in embodiments;

FIG. 4a-4e show examples of five angular intra-picture prediction anglesfor a 4×2 block of prediction samples according to embodiments;

FIG. 4f shows a schematic diagram for illustrating an of a direction ofan angular prediction used in embodiments;

FIG. 4g-4h show tables for illustrating example dependencies of a numberof taps used in filters, the number being dependent from a block size ofthe prediction block and from the prediction mode;

FIG. 5a-5c show an embodiment in connection with an angular predictionusing a definition of an angle parameter;

FIG. 6a-6c show a derivation of a vertical offset in connection withmapping reference samples according to embodiments;

FIG. 7a-7c show a derivation of a horizontal offset according to anembodiment;

FIG. 8 shows an embodiment for a diagonal top-left angle and a use ofnearest reference samples according to an embodiment;

FIG. 9 shows an example projection of extended left reference samples asside reference next to the extended top reference samples as mainreference in case of top-left diagonal prediction according to anembodiment;

FIG. 10 shows an example projection of nearest left reference samples asside reference next to the extended top reference samples according toan embodiment;

FIG. 11 shows an example truncated unary code for a specific set ofreference areas according to an embodiment;

FIG. 12a-b show a schematic illustration of usable block sizes accordingto embodiments;

FIG. 13 shows a schematic diagram according to an embodiment of verticalangular prediction with an angle of 45 degree of a prediction block; and

FIG. 14a-b show an example of needed nearest reference samples andextended reference samples in case of diagonal vertical intra-pictureprediction and according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Equal or equivalent elements or elements with equal or equivalentfunctionality are denoted in the following description by equal orequivalent reference numerals even if occurring in different figures.

In the following description, a plurality of details is set forth toprovide a more thorough explanation of embodiments of the presentinvention. However, it will be apparent to those skilled in the art thatembodiments of the present invention may be practiced without thesespecific details. In other instances, well known structures and devicesare shown in block diagram form rather than in detail in order to avoidobscuring embodiments of the present invention. In addition, features ofthe different embodiments described hereinafter may be combined witheach other, unless specifically noted otherwise.

In hybrid video coding, intra-picture prediction is used to encode anarea of picture samples by generating a prediction signal from availableneighboring samples, i.e. the reference samples. The prediction signalis subtracted from the original signal to get the residual signal. Thisresidual signal or prediction error is further transformed, scaled,quantized and entropy coded as illustrated in FIG. 1 showing a schematicblock diagram of a video encoder 1000 according to an embodiment being,for example, a hybrid video encoder with an intra-picture predictionblock 1001. The video encoder 1000 is configured to receive an inputvideo signal 1002 comprising a plurality of pictures, a sequence ofpictures forming a video. The video encoder 1000 comprises a block 1004being configured to divide the signal 1002 into an area of samples,i.e., to form blocks from the input video signal 1002. A controller 1006of the video encoder 1000 is configured to control the block 1004 and tocontrol a decoder 1008 that may be a part of the encoder 1000. A decoderfor receiving and decoding an output bitstream 1012 and a generatedoutput video signal 1014, i.e., coding data, may be implementedaccordingly. In particular, a transform, scaling and quantization block1016 together with a block 1018 for motion estimation of the signal 1022being the input video signal 1002 divided into blocks by the block 1004may both provide information in terms of quantized transformcoefficients and a motion information so as to enable entropy coding forthe output bitstream 1012.

The quantized transformed coefficients are then scaled and inversedtransformed to generate the reconstructed residual signal beforepotential in-loop filtering operations. This signal can be added to theprediction signal again to get the reconstruction that is also availableat the decoder. The reconstructed signal can be used to predictsucceeding samples in coding order within the same picture.

The intra-picture prediction is further detailed in FIG. 2. First, thereference samples used for the prediction are generated in a block 1042based on the reconstructed samples. This stage also includessubstituting neighboring samples that are not available, e.g. atpicture, slice or tile boundaries. Second, in a block 1044 the referencesamples can be filtered to eliminate discontinuities in the referencesignal. Third, in a block 1046 the prediction samples are calculatedusing the reference samples according to the intra prediction mode. Theprediction mode describes how the prediction signal is generated fromthe reference samples, e.g. by averaging them in the DC mode or bycopying them along one prediction angle in an angular prediction mode.The encoder has to decide which intra prediction mode to select and theselected intra prediction mode is signaled in the bitstream by entropycoding to the decoder. At the decoder side, the intra prediction mode isextracted from the bitstream by entropy decoding. Fourth and possiblylast, in a block 1048 the prediction samples can be filtered as well tosmoothen the signal. In other words, FIG. 2 shows a flowchart of anintra-picture prediction process or method. In general, the correlationbetween samples in an image decreases with increasing distance. Hencedirectly neighboring samples are generally well suited as referencesamples to predict an area of samples. However, there are cases wherethe directly neighboring reference samples represent an edge or anobject in a uniform area (occlusion). In these cases, the correlationbetween the samples to predict (uniform or textured area) and thedirectly neighboring reference samples (edge) would be low. Extendedreference intra-picture prediction solves this problem by incorporatingmore distant reference samples that are not directly neighboring. Theconcept of extending the nearest reference samples is known but severalnovel improvements for all parts of the intra-picture prediction processand signaling are defined in embodiments of the present invention anddescribed in the following.

Extended reference intra-picture prediction allows to generate theprediction signal of a sample area using extended references samples.Extended reference samples are available reference samples that are notdirect neighbors. In the following, improved reference samplegeneration, filtering, prediction and prediction filtering usingextended reference samples according to embodiments are described infurther detail. The special case of combining predictions using extendedreference samples with prediction using directly neighboring samples orunfiltered reference samples is covered in afterwards. After that,various methods according to embodiments are described to improveprediction mode and extended reference area signaling for extendedreference samples. Further, embodiment to facilitate parallel encodingwith extended reference samples are described.

For reference sample generation, current video coding standards usedirectly neighboring samples to predict the current block. Inliterature, it was proposed to use multiple reference lines in additionto the nearest, directly neighboring samples. The additional referencelines to be used in intra-picture prediction are further referred to asextended reference samples in detailed in the following.

After that, improved methods for substitution of non-available extendedreference samples according to embodiments are described.

An example showing a nearest reference sample line and three extendedreference sample lines of a 16×8 block to be predicted is illustrated inFIG. 3 showing an example of directly neighboring (nearest) referencesamples 1062 and extended reference samples 10641, 10642 and 10643.

The nearest reference samples 1062 and the extended reference samples10641, 10642 and 10643 are arranged adjacent to a prediction block 1066to be predicted and being arranged along two directions of the picture,namely direction x and direction y being arranged perpendicular todirection x. Along the direction x, the prediction block comprises anextension W with samples ranging from 0 to W−1. Along the direction y,the prediction block comprises an extension H with samples ranging from0 to H−1.

A reference area with index i may indicate a distance between therespective reference sample, i.e., the nearest reference sample havingindex i=0, i.e., being arranged directly adjacent, and extendedreference samples being spaced from the prediction block 1066 at leastby the nearest reference samples 1062. For example, the reference areaindex i may indicate an extension of a distance between the predictionblock 1066 and the respective reference sample 1062 or 1064. By way ofexample, increasing parameter x along the direction x may be referred toas moving right and, on the contrary, reducing the x may be referred toas moving left.

Alternatively or in addition, reducing the index i along a negativedirection y may be referred to as moving upwards or towards a top of thepicture, wherein with an increase of parameter y, a movement downwardsor towards a bottom of the picture may be indicated. Terms like top,bottom, left and right are used to simplify the understanding of thepresent invention. According to other embodiments, such terms may bechanged, altered or substituted with any other directions withoutlimiting the scope of the present embodiments. By way of example,reference samples 1062 and/or 1064 being arranged left from theprediction block, i.e., having x<0, may be referred to as left referencesamples. Reference samples 1062 and/or 1064 being arranged so as to have_(y)<0 may be referred to as top reference samples, assuming that anupper left edge of the prediction block 1066 has positions 0,0.Reference samples being identified as well as left reference samples andas top reference samples may be referred to as corner reference samples.Accordingly, reference samples exceeding the extension W along thex-direction may be referred to as right reference samples, whereinreference samples exceeding the extension H of the prediction block 1066may be referred to as bottom reference samples.

In order to indicate which reference samples to use for prediction, eachline of reference samples is associated with a reference area index i.The nearest reference samples are given an index i=0, the next line ofextended reference samples i=1 and so on. Using the notation from FIG.3, the top reference samples can be described by r(x, −1−i) with xranging from 0 to M and the left reference samples can be described byr(−1−i, y) with y ranging from 0 to N. The parameters M for thehorizontal extend and N for the vertical extend of the reference samplesdepend on the intra-picture prediction. In case top-right diagonalprediction is used as maximum angle clockwise for example as describedin connection with FIG. 4e , the top reference samples need to extentM=W+H−1+i samples in horizontal direction. In case bottom-left diagonalprediction is used as maximum angle counter clockwise for example asdescribed in FIG. 4a , the left reference samples need to extentM=H+W−1+i samples in vertical direction. As in FIG. 3, W describes thewidth and H the height of the prediction block.

A video encoder according to an embodiment, such as video encoder 1000may be configured to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction. The video encoder mayuse, in the intra-picture prediction, for encoding a prediction block ofa picture, a plurality of extended reference samples of the picture,each extended reference sample of the plurality of extended referencesamples separated from the prediction block at least by one nearestreference sample of the plurality of reference samples, directlyneighboring the prediction block. The video encoder may sequentiallydetermine an availability or unavailability of each of the plurality ofnearest reference samples and may substitute a nearest reference samplebeing determined as unavailable by a substitution sample. The videoencoder may use the substitution sample for the intra-pictureprediction.

For determining the availability or unavailability, the video encodermay check the samples sequentially according to a sequence, determinethe substitution sample as a copy a last extended reference sample beingdetermined as available in the sequence; and/or determine thesubstitution sample as a copy a next extended reference sample beingdetermined as available in the sequence.

The video encoder may further determine the availability orunavailability sequentially according to a sequence and determine thesubstitution sample based on a combination of an extended referencesample being determined as available and being arranged in the sequenceprior to the reference sample being determined as unavailable and of anextended reference sample being determined as available and beingarranged in the sequence after the reference sample being determined asunavailable.

Alternatively or in addition, the video encoder may be configured touse, for the intra-picture prediction, for encoding a prediction blockof a picture, a plurality of nearest reference samples of the picturedirectly neighboring the prediction block and a plurality of extendedreference samples, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples;and to determine an availability or unavailability of each of theplurality of extended reference samples. The video encoder may signal ause of the plurality of extended reference samples when a portion ofavailable extended reference samples of the plurality of extendedreference samples is larger than or equal a predetermined threshold; andskip signaling the use of the plurality of extended reference sampleswhen the portion of available extended reference samples of theplurality of extended reference samples is below the predeterminedthreshold.

A respective decoder such as video decoder 1008 or a video decoder forgenerating a video stream again, may accordingly be configured todecode, by block based predictive decoding, pictures coded in codingdata into a video, wherein the block based predictive decoding comprisesan intra-picture prediction; to use, in the intra-picture prediction,for encoding a prediction block of a picture, a plurality of extendedreference samples of the picture, each extended reference sample of theplurality of extended reference samples separated from the predictionblock at least by one nearest reference sample of the plurality ofreference samples, directly neighboring the prediction block; and tosequentially determine an availability or unavailability of each of theplurality of extended reference samples. The video decoder maysubstitute an extended reference sample being determined as unavailableby a substitution sample; and use the substitution sample for theintra-picture prediction.

The video decoder may further be configured to determine theavailability or unavailability sequentially according to a sequence;determine the substitution sample as a copy a last extended referencesample being determined as available in the sequence; and/or determinethe substitution sample as a copy a next extended reference sample beingdetermined as available in the sequence.

Further, the video decoder may be configured to determine theavailability or unavailability sequentially according to a sequence; andto determine the substitution sample based on a combination of anextended reference sample being determined as available and beingarranged in the sequence prior to the reference sample being determinedas unavailable and of an extended reference sample being determined asavailable and being arranged in the sequence after the reference samplebeing determined as unavailable.

The video decoder may alternatively or in addition be configured to use,for the intra-picture prediction, for decoding a prediction block of apicture, a plurality of nearest reference samples of the picturedirectly neighboring the prediction block and a plurality of extendedreference samples, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples;to determine an availability or unavailability of each of the pluralityof extended reference samples; to signal receive information indicatinga use of the plurality of extended reference samples when that a portionof available extended reference samples of the plurality of extendedreference samples is larger than or equal a predetermined threshold anduse of the plurality of extended reference samples; and to skip usingthe plurality of extended reference samples in absence of theinformation, i.e., when the portion of available extended referencesamples of the plurality of extended reference samples is below thepredetermined threshold.

When neighboring reference samples are not available, according toembodiments, an extended reference sample substitution may be performed.For example, the unavailable samples can be replaced by the closestneighboring sample that is available, a combination of the closest twoor by a predetermined value in case there are no neighboring samplesavailable, e.g. 2^(bitdepth-1). Reference samples are not available e.g.when they are located outside a picture, slice or tile boundary or whenconstrained intra prediction is used that disallows using samples frominter-picture predicted areas as reference for intra-picture predictionareas.

For example, if the current block to be predicted is located at the leftpicture boundary. the left and top-left corner reference samples are notavailable. In this case, the left and top-left corner reference samplesare substituted by the first available top reference sample. When thisfirst available top reference sample is the first one, i.e. r(0, −1−i),the substitution for nearest (i=0) and extended (i>0) reference samplescan be formulated as follows:

r(−1−i,y)=r(0,−1−i) with y=−1−i . . . M

r(x,−1−i)=r(0,−1−i) with y=−1−i . . . M for i>0

The parameter i may have any maximum value larger than 0 within theencode/decoder system, e.g., 1, 2, 3, 4 or more such as 5 or more or 10or more.

When constrained intra prediction is used, it can happen that one ormore neighboring blocks are not available because they are coded usinginter-picture prediction. For example, the left H samples r(−1−i, y)with y=0 . . . H−1 are inside an inter-picture predicted block and notavailable because constrained intra prediction is enabled.

In one embodiment, the availability checking process for each referencesample is done sequentially, e.g. from the bottom-left to the top-rightreference samples or vice versa, the first sample that is not availablealong this direction is replaced by the last one that is available ifthere is one. If there is no sample available before, the unavailablesamples are replaced by the next available sample. In the embodimentstarting from bottom-right, the W bottom-right samples r (−1−i, y) withy=H . . . W−1 are available. Consequently, the left samples are replacedby as follows:

r(−1−i,y)=r(−1−i,M) with y=0 . . . M−1

In another embodiment, unavailable reference samples between availablereference samples could be generated by linearly interpolating betweenthe two nearest samples, one from each side.

In case it is determined that most of the extended reference areasamples are not available, the use of extended reference samples doesnot bring any benefit compared to using the nearest reference samples.Hence the signaling of the reference area index can be saved and itssignaling can be restricted to blocks where at least half of theextended reference samples are available.

A video encoder according to an embodiment such as video encoder 1000may be configured to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, in theintra-picture prediction, for encoding a prediction block of a picture,a plurality of extended reference samples of the picture, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples, directly neighboring theprediction block; to filter at least a subset of the plurality ofextended reference samples using a bilateral filter so as to obtain aplurality of filtered extended reference samples; and to use theplurality of filtered extended reference samples for the intra-pictureprediction.

The video encoder according to this embodiment may be configured tocombine the plurality of filtered extended reference samples with aplurality of unfiltered extended reference samples so as to obtain aplurality of combined reference values, wherein the video encoder isconfigured to use the plurality of combined reference values for theintra-picture prediction.

Alternatively or in addition, the video encoder may be configured tofilter the plurality of extended reference samples using one of a 3-tapfilter, a 5-tap filter and a 7-tap filter.

The video encoder may further be configured to select predict theprediction block using an angular prediction mode; wherein the 3-tapfilter, a 5-tap filter and a 7-tap filter are configured as bilateralfilters, wherein the video encoder is configured to select to use one ofthe 3-tap filter, the 5-tap filter and the 7-tap filter based on anangle used for the angular prediction, the angle arranged between ahorizontal or a vertical direction of the angular prediction mode;and/or wherein the video decoder is configured to select to use one ofthe 3-tap filter, the 5-tap filter and the 7-tap filter based on a blocksize of the prediction block. As shown in FIG. 4f , an angle ε maydescribe an angle of a direction of an angular prediction used forpredicting the prediction block 1066 with respect to horizontal borders1072 and/or vertical borders 1074 of the prediction block 1066 andmeasured towards a diagonal 1076 between the horizontal and verticaldirection, i.e., the angle of the angular prediction is at most 45°.With increasing angle ε an increased number of taps may be used in thefilter. Alternatively or in addition, a block size may define a basis ordependency for selecting the filter.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to use, in the intra-picture prediction, for decoding aprediction block of a picture, a plurality of extended reference samplesof the picture, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples,directly neighboring the prediction block; to filter at least a subsetof the plurality of extended reference samples using a bilateral filterso as to obtain a plurality of filtered extended reference samples; andto use the plurality of filtered extended reference samples for theintra-picture prediction.

The video decoder may further be configured to combine the plurality offiltered extended reference samples with a plurality of unfilteredextended reference samples so as to obtain a plurality of combinedreference values, wherein the video decoder is configured to use theplurality of combined reference values for the intra-picture prediction.

Alternatively or in addition, the video decoder of may be configured tofilter the plurality of extended reference samples using one of a 3-tapfilter, a 5-tap filter and a 7-tap filter. As described for the encoder,the 3-tap filter, a 5-tap filter and a 7-tap filter are configured asbilateral filters, wherein the video decoder is configured to predictthe prediction block using an angular prediction mode, and to select touse one of the 3-tap filter, the 5-tap filter and the 7-tap filter basedon an angle used for the angular prediction, the angle arranged betweena horizontal or a vertical direction of the angular prediction mode;and/or wherein the video decoder is configured to select to use one ofthe 3-tap filter, the 5-tap filter and the 7-tap filter based on a blocksize of the prediction block.

For example, instead of a bilateral filter, 3-tap FIR filters may beused. This may allow to filter only the nearest reference samples(although not with bilateral filter) and to leave the extended referencesamples unfiltered.

For larger sample areas, discontinuities in the reference samples canoccur that distort the prediction. The state of the art solution to thisis to apply linear smoothing filters to the reference samples. In caseof discontinuities, which can be detected for example by comparing to apredetermined threshold, strong smoothing can be applied. This typicallygenerates the reference samples by interpolating between cornerreference samples.

However, linear smoothing filters can also remove edge structure thatneeds to be preserved. Applying bilateral filters to the extendedreferences samples according to an embodiment for reference samplefiltering can prevent undesired smoothing of sharp edges. Sincebilateral filtering is more efficient for larger blocks and intraprediction angles that deviate from the exact horizontal and exactvertical directions, the decision of whether to apply the filter and thelength of the filter can depend on the block size and/or the predictionmode. One example design can incorporate dependencies as shown in FIG.4g showing a dependency for block sizes smaller than 64×64 and largerthan or equal to 64×64 with respect to W×H and FIG. 4h showing adifferent dependency for block sizes smaller than 64×64 and larger thanor equal to 64×64 with respect to W×H. In the embodiment of FIG. 4g theintra-prediction mode may, for example, one of a planar mode, a DC mode,a near horizontal mode, a near vertical mode or a different angle of anangular mode. In the embodiment of FIG. 4h , additionally angles beingidentified as farer horizontal and farer vertical may be selected, forexample, having a larger value of angle ε shown in FIG. 4f when comparedto near horizontal or near vertical. As may be seen, larger block sizesmay result in a higher number of taps so as to facilitate filtering ofthe larger amount of data, wherein, additionally, an increase of ε mayalso result in an increase of taps. According to FIG. 4h , an embodimentmay apply a small 3-tap filter for near horizontal and near verticalmodes and increases the filter length with increasing distance fromhorizontal and vertical direction. Although being illustrated as beingdependent on both, the prediction mode and the block size, the selectionof the filter or at least the number of taps may alternatively dependonly on one of both and/or on additional parameters.

In another embodiment for reference sample filtering, an intra-pictureprediction that uses filtered reference samples can be combined withunfiltered reference samples using a position-dependent weighting asdescribed in connection with Position Depending Prediction Combination.In this case, the reference samples for the prediction that usesfiltered references samples can use a different reference samplefiltering than for the non-combined prediction. For example, thefiltering can select among a set of 3-, 5- and 7-tap filters.

A video encoder according to an embodiment such as video encoder 1000may be configured to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, in theintra-picture prediction, for encoding a prediction block of a picture,a plurality of extended reference samples of the picture, each extendedreference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples, directly neighboring theprediction block, wherein a plurality of nearest reference samples isarranged along a first picture direction of the prediction block andalong a second picture direction of the prediction block; to map atleast a part of the nearest reference samples arranged along the seconddirection to extended reference samples being arranged along the firstdirection, such that the mapped reference samples exceed an extension ofthe prediction block along the first picture direction; and; and to usethe mapped extended reference samples for the prediction.

The video encoder may further be configured to map the portion ofnearest reference samples according to a prediction mode used forpredicting the prediction block. The video encoder may be configured tomap the portion of nearest reference samples according to a directionused in the prediction mode for predicting the prediction block.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to use, in the intra-picture prediction, for decoding aprediction block of a picture, a plurality of extended reference samplesof the picture, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples,directly neighboring the prediction block, wherein a plurality ofnearest reference samples is arranged along a first picture direction ofthe prediction block and along a second picture direction of theprediction block;

map at least a part of the nearest reference samples arranged along thesecond direction to extended reference samples being arranged along thefirst direction, such that the mapped reference samples exceed anextension of the prediction block along the first picture direction; andto use the mapped extended reference samples for the prediction.

The video decoder may be configured to map the portion of nearestreference samples according to a prediction mode used for predicting theprediction block. The video decoder may be configured to map the portionof nearest reference samples according to a direction used in theprediction mode for predicting the prediction block.

In principle, every intra-picture prediction that uses the directlyneighboring reference samples can be adapted to use the extendedreference samples. In literature, the following three predictions havebeen adapted

-   -   Planar    -   DC    -   Angular

In the following each prediction will be detailed for extended referencesamples to thereby describe embodiments of the present invention.

The planar prediction is a bilinear interpolation of the W×H predictionsamples illustrated in FIG. 3 from the boundaries. Since the right andbottom boundaries are not yet reconstructed, the right boundary samplesare set equal to the top-right corner sample r(W, −1) and the bottomboundary samples are set equal to the bottom-left corner sample r(−1,H):

${p\left( {x,y} \right)} = \frac{{W \cdot {p_{ver}\left( {x,y} \right)}} + {H \cdot {p_{hor}\left( {x,y} \right)}} + {W \cdot H}}{2{W \cdot H}}$with  x = 0  …  W − 1, y = 0  …  H − 1p_(ver)(x, y) = (H − 1 − y) ⋅ r(x, −1) + (y + 1) ⋅ r(−1, H)p_(hor)(x, y) = (W − 1 − x) ⋅ r(−1, y) + (x + 1) ⋅ r(W, −1)

For extended reference samples, the vertical and horizontal predictionsp_(ver) and p_(hor) depend on the reference area index i:

p _(ver,i)(x,y)=(H−1−y)·r(x,−1−i)+(y+1)·r(−1−i,H)

p _(hor,i)(x,y)=(W−1−x)·r(−1−i,y)+(x+1)·r(W,−1−i)

One embodiment to improve extended reference samples is to use thenearest top-right corner sample r(W, −1) and the nearest bottom-leftcorner sample r(−1, H) in vertical and horizontal predictions p_(ver,i)and p_(hor,i) as follows:

p _(ver,i)(x,y)=(H−1−y)·r(x,−1−i)+(y+1)·r(−1−1,H)

p _(hor,i)(x,y)=(W−1−x)−r(−1−i,y)+(x+1)−r(W,−1)

Another embodiment defines to include the corner reference samples inthe horizontal and vertical predictions as well with distance-dependentweighting. The farer away the extended reference area gets, i.e. thelarger the parameter i gets, the more top-left corner samples areavailable for the prediction. For i=0 it is one sample r(−1, −1), i.e.,adjacent to the prediction block or with distance 0, for i>0 there are ivertical corner samples r(−1−i,y) with y=−1 . . . −1−i, i horizontalcorner samples r(x, −1−i) with x=−1 . . . −1−i and the corner sampler(−1−i, −1−i). One implementation according to an embodiment defines toaverage the horizontal and vertical corner samples (both including thecorner sample) and include it with a distance-dependent weighting by a() and b( ) in the vertical and horizontal predictions be as follows:

${p_{{ver},i}\left( {x,y} \right)} = {{{{a(y)}\frac{\sum_{x_{0} = {- 1}}^{{- 1} - i}{r\left( {x_{0},{{- 1} - i}} \right)}}{i + 1}} + {{b(y)} \cdot {r\left( {x,{{- 1} - i}} \right)}} + {{\left( {y + 1} \right) \cdot {r\left( {{{- 1} - i},H} \right)}}\mspace{14mu} {with}\mspace{14mu} {a(y)}} + {b(y)}} = \left( {H - 1 - y} \right)}$${p_{{hor},i}\left( {x,y} \right)} = {{{{a(x)}\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}} + {{b(x)} \cdot {r\left( {{{- 1} - i},y} \right)}} + {{\left( {x + 1} \right) \cdot {r\left( {W,{{- 1} - i}} \right)}}\mspace{14mu} {with}\mspace{14mu} {a(x)}} + {b(x)}} = \left( {W - 1 - x} \right)}$

Another embodiment is a combination of the two previous embodimentsusing the nearest top-right sample, the nearest bottom-left sample andthe extended corner samples.

The DC prediction calculates the average of the reference sample valuesDC and sets every prediction sample p(x, y) inside a W×H block equal tothe average:

p(x,y)=DC with x=0 . . . W−1,y=0 . . . H−1

For the average value DC, only N samples left and M samples right to theprediction block can be used where N can be set to the height H and Mcan be set to the width W:

${DC} = {\frac{1}{M + N}\left( {{\sum\limits_{n = 0}^{N - 1}{r\left( {{- 1},n} \right)}} + {\sum\limits_{m = 0}^{M - 1}{r\left( {m,{- 1}} \right)}}} \right)}$

For extended reference samples, the average value DC depend on thereference area index i:

${DC_{i}} = {\frac{1}{M + N}\left( {{\sum\limits_{n = 0}^{N - 1}{r\left( {{{- 1} - i},n} \right)}} + {\sum\limits_{m = 0}^{M - 1}{r\left( {m,{{- 1} - i}} \right)}}} \right)}$

In one embodiment, the corner sample(s) to the top left of theprediction block can be used in the average as well:

${DC_{i}} = {\frac{1}{M + N + 1 + {2i}}\left( {{\sum\limits_{n = {- i}}^{N - 1}{r\left( {{{- 1} - i},n} \right)}} + {\sum\limits_{m = {{- i} - 1}}^{M - 1}{r\left( {m,{{- 1} - i}} \right)}}} \right)}$

Angular prediction calculates the prediction samples by deriving themalong a specified direction or angle. The simplest prediction directionsare horizontal, vertical and three diagonal ones which are illustratedin FIG. 4a to FIG. 4e showing examples of five angular intra-pictureprediction angles for a 4×2 block of prediction samples. It can be seenthat the reference samples along each direction point to a full(integer) sample position. The modification for extended referencesamples (in green) as described in literature is straightforward andjust extends the direction. Although the size of the block of predictionsamples is 4×2, angular intra prediction can be extended to arbitraryblock sizes.

According to embodiments, a finer prediction angle granularity may beused, such that a direction can point to non-integer samples positions.These may be generated by interpolation using the nearest integer samplepositions. Interpolation can be done using a simple bilinear filter ormore advanced filters, for example cubic or Gaussian 4-tap filters.

For the prediction angles between horizontal and vertical, e.g. thediagonal top-left angle and all angles in between, reference samplesfrom the left and top are used to generate the prediction. A referencesample projection may be used to facilitate such generation. For allvertical angles between diagonal top-left and vertical, the topreference samples can be seen as the main reference and the left samplescan be seen as side reference. For all horizontal angles betweenhorizontal and diagonal top-left, the left reference samples can be seenas the main reference and the top reference sample can be seen as theside reference. In order to simplify the computation, i.e. to not switchbetween main reference sample calculation and side reference samplecalculation, the side reference samples are projected along theprediction angle to extend the line of main reference samples. Eachreference sample r(x, −1) left to the top main reference or r(−1,y)above the left main reference is projected onto a corresponding sidereference sample according to the inverse prediction angle. Depending onthe prediction angle, the projection can point to a sub-sample position.

FIG. 5a to FIG. 5c show an embodiment in connection with an angularprediction using a definition of an angle parameter A given in 1/32sample accuracy for the top-left diagonal prediction angle and two othervertical angles. The following embodiment assumes 1/32 sample accuracyand vertical prediction angles between vertical and top-left diagonal,wherein any other vales may be implemented. The 33 prediction anglesrange can be described by an angle parameter A ranging from 0 (vertical)to 32 (top-left diagonal) as illustrated in FIG. 5a to FIG. 5c . A maybe referred to as a distance along a second picture direction withrespect to a given first picture extension such as 32 samples. In FIG.5a A is 32 samples, i.e., 32 resulting in an angle of 45° based on apicture extension of 32 samples along the picture directionperpendicular to A. In FIG. 5b , A=17 and in FIG. 5c , A=1.

Based on the angle parameter A, the vertical offset verOffset(x) intothe left side reference column for each main reference sample r(x, −1)can be calculated as follows:

${{verOffset}(x)} = {\left( {{x*{round}\mspace{14mu} \left( \frac{256*32}{A} \right)} + {128}} \right)8}$r(−1 − x, −1) = r(−1, −1 + verOffset(x))with  x = 1  …  max Offset − 1${\max {Offset}} = {{ceil}\left( \frac{A*H}{32} \right)}$

The derivation of the vertical offset verOffset(x) and the maximumhorizontal offset maxOffset based on the parameter A is illustrated inFIG. 6a to FIG. 6c and FIG. 7a to FIG. 7c , wherein FIG. 6a to FIG. 6cshow a calculation of the vertical offset given horizontal displacementx for top-left horizontal prediction angles with A=32, 17, 1 accordingto FIG. 5a to FIG. 5 c.

FIG. 7a to FIG. 7c show a calculation of maximum horizontal offsetmaxOffset given the height H of the prediction block for top-lefthorizontal prediction angles with A=32, 17, 1.

In the embodiment, the nearest integer reference sample is used insteadof the sub-sample position by rounding the vertical offset. Thisfacilitates the computation. However, it is also possible to project theinterpolated sub-sample side reference sample.

FIG. 8 shows an embodiment for the diagonal top-left angle (A=17) andthe nearest reference samples. With a height of eight samples (H=8), itcan be seen that four (maxOffset−1) left reference samples can beprojected along the diagonal direction to extend the main referencesample line, i.e. nearest top reference samples. According toembodiments the illustrated size of pictures, blocks, slices or the likeare given as example only and may comprise any other values.

FIG. 8 shows an example projection of nearest left reference samples asside reference next to the nearest top reference samples as mainreference in case of a top-left horizontal direction with angleparameter A=17 according to an embodiment.

For extended reference samples with reference area index i, theprojection can be adapted as follows:

${{verOffset}(x)} = {\left( {{x*{round}\mspace{14mu} \left( \frac{256*32}{A} \right)} + {128}} \right)8}$r(−1 − i − x, −1 − i) = r(−1 − i, −1 + verOffset(x))with  x = 1  …  max Offset − 1${\max {Offset}} = {{{ceil}\left( \frac{A*\left( {H + i} \right)}{32} \right)} - i}$

FIG. 9 shows the embodiment for the diagonal top-left angle (A=17) and aheight of eight samples (H=8) using the extended reference line withi=3. Here, two (maxOffset−1) left reference samples can be projectedalong the diagonal direction to extend the main reference sample line,i.e. nearest top reference samples.

FIG. 9 shows an example projection of extended left reference samples asside reference next to the extended top reference samples as mainreference in case of top-left diagonal prediction with angle parameterA=17 according to an embodiment.

When reference samples from the left and top are used, extendedreference samples allow to combine nearest and extended referencessamples. This embodiment of the straight-forward approach from FIG. 9allows to make use of the extended references samples along the maindirection, i.e. main reference, where the larger distance of referencesamples can be beneficial in case of occlusion or an edge on the nearestreference samples. However, for the side reference the correlationbetween the samples to be predicted and the nearest reference samplescan be higher than between the extended reference samples and thesamples to be predicted.

For example, one way to combine the extended main reference samples r(x,−1−i) with the nearest side reference samples r(−1, y) can be formulatedas follows:

${{verOffset}(x)} = {\left( {{x*{round}\mspace{14mu} \left( \frac{256*32}{A} \right)} + {128}} \right)8}$r(−1 − i − x, −1 − i) = r(−1 − i, −1 + verOffset(x))with  x = 1  …  max Offset − 1  and  verOffset(x) > i${\max {Offset}} = {{ceil}\left( \frac{A*\left( {H + i} \right)}{32} \right)}$

This combination is illustrated in FIG. 10 based on the same embodimentas described in connection with the previous figures. Here, the extendedreference samples 10643 arranged in a line are used for the mainreference samples (top) within the prediction direction (vertical) whilethe nearest reference samples 1062 arranged in a column can be used forthe side reference samples that are projected to the extended referencesample line (top row) along the prediction direction to extend the mainreference sample line.

FIG. 10 shows an example projection of nearest left reference samples asside reference next to the extended top reference samples as mainreference in case of top-left diagonal prediction with angle parameterA=17. According to the embodiment of FIG. 10, nearest reference samplesare used as source for generating extended reference samples, i.e., thenearest reference samples are mapped to extended reference samples.Alternatively, extended reference samples may be mapped to extendedreference samples, see FIG. 9.

A video encoder according to an embodiment such as video encoder 1000may be configured to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, for theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and a plurality of extended referencesamples, each extended reference sample of the plurality of extendedreference samples separated from the prediction block at least by onenearest reference sample of the plurality of reference samples. Thevideo encoder is configured to boundary filtering in a mode where noextended samples are used; and not to use boundary filtering whenextended samples are used; or to boundary filtering at least a subset ofthe plurality of nearest reference samples and not using boundaryfiltering for the extended samples.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for decoding aprediction block of a picture, a plurality of nearest reference samplesof the picture directly neighboring the prediction block and a pluralityof extended reference samples, each extended reference sample of theplurality of extended reference samples separated from the predictionblock at least by one reference sample of the plurality of referencesamples. The video decoder is configured to boundary filtering in a modewhere no extended samples are used; and not to use boundary filteringwhen extended samples are used; or to boundary filtering at least asubset of the plurality of nearest reference samples and not usingboundary filtering for the extended samples.

Since the extended reference samples are not directly neighboring theprediction sample, discontinuities on specific block boundaries may notbe as severe as when the nearest reference samples are used. Therefore,it is beneficial to perform a prediction filtering according to:

-   -   Not perform boundary filtering operations in case extended        reference samples are used, or    -   Modify boundary smoothing by using the nearest reference samples        instead of the extended reference samples.

With the extended predictions, it is possible to combine predictionsfrom nearest and extended reference samples so as to obtain a combinedprediction. In literature, a fixed combination of a prediction using thenearest reference samples with a prediction using extended referencesamples with predetermined weights is described. In this case bothprediction use the same prediction mode for all reference areas andsignaling the mode also signals the combination of the predictions. Onone hand this reduces the signaling overhead to indicate the referencesample area but it also removes the flexibility to combine two differentprediction modes with two different reference samples areas. Possiblecombinations that allow for more flexibility are detailed in thefollowing.

A video encoder according to an embodiment such as video encoder 1000may be configured to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to determine, in theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and a plurality of extended referencesamples, each extended reference sample of the plurality of extendedreference samples separated from the prediction block at least by onenearest reference sample of the plurality of reference samples; todetermine a prediction for the prediction block using the extendedreference samples; to filter the extended reference samples so as toobtain a plurality of filtered extended reference samples. The videoencoder is configured to combine the prediction and the filteredextended reference samples so as to obtain a combined prediction for theprediction block.

The video encoder may be configured to combine the prediction andextended reference samples being arranged in a major diagonal or minordiagonal of samples with respect to the prediction block.

The video encoder may be configured to combine the prediction and theextended reference samples based on the determination rule:

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} + {\frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}r\left( {{{- 1} - i},y} \right)} -} \\{{{\frac{c_{2}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} + {{b\left( {x,y} \right)} \cdot {p\left( {x,y} \right)}} + 64}\quad}\end{matrix}}{128\quad}$

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and r(−1−i,−1−i) for i>0 is an extended cornerreference sample of the plurality of extended reference samples withrespect to a boundary of the prediction block and b(x,y) denotes anormalization factor.

The normalization factor may be determined based on the determinationrule:

${b\left( {x,y} \right)} = {{128} - \frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}} + \frac{c_{2}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}} - \frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}} + \frac{c_{2}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}}$

The video encoder may be configured to filter the extended referencesamples so as to obtain filtered extended reference samples (r(x,−1−i),r(−1−i,y), r(−1−i,−1−i) for i>0) (combined) using one of a 3-tap filter,a 5-tap filter and a 7-tap filter and to use the filtered extendedreference samples for the prediction.

The video encoder may be configured to use a combination of extendedcorner reference samples of the prediction block and of extendedreference samples being arranged in a corner region of reference samples(r(−1−i,−1−i)).

The video encoder may be configured to obtain the combined predictionbased on the determination rule:

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} -} \\{{\frac{c_{2}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}\frac{\sum_{x_{0} = {- 1}}^{{- 1} - i}{r\left( {x_{0},{{- 1} - i}} \right)}}{i + 1}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}} + {b{\left( {x,y} \right) \cdot {p\left( {x,y} \right)}}} + 64}\end{matrix}}{128\quad}$

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and

$\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}$

for i>0 are the combined extended corner reference samples with respectto a boundary of the prediction block and b(x,y) denotes a normalizationfactor.

The video encoder may be configured to obtain the prediction p(x,y)based on an intra-picture prediction.

The video encoder may be configured to use only planar prediction asintra-picture prediction.

The video encoder may be configured, for each encoded video block, todetermine a parameter set identifying the combination of the predictionand the filtered extended reference samples. The video encoder may beconfigured to determine the parameter set identifying the combination ofthe prediction and the filtered extended reference samples using alook-up table containing sets for different block sizes of theprediction block.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to determine, in the intra-picture prediction, for decodinga prediction block of a picture, a plurality of nearest referencesamples of the picture directly neighboring the prediction block and aplurality of extended reference samples, each extended reference sampleof the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples; to determine a prediction for theprediction block using the extended reference samples; to filter theextended reference samples so as to obtain a plurality of filteredextended reference samples; and to combine the prediction and thefiltered extended reference samples so as to obtain a combinedprediction for the prediction block.

The video decoder may be configured to combine the prediction andextended reference samples being arranged in a major diagonal or minordiagonal of samples with respect to the prediction block.

The video decoder may be configured to combine the prediction and theextended reference samples based on the determination rule:

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} + {\frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}r\left( {{{- 1} - i},y} \right)} -} \\{{\frac{c_{2}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} + {b{\left( {x,y} \right) \cdot {p\left( {x,y} \right)}}} + 64}\end{matrix}\quad}{128\quad}$

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and r(−1−i,−1−i) for i>0 is an extended cornerreference sample of the plurality of extended reference samples withrespect to a boundary of the prediction block and b(x,y) denotes anormalization factor.

The normalization factor may be determined based on the determinationrule:

${b\left( {x,y} \right)} = {{128} - \frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}} + \frac{c_{2}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}} - \frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}} + \frac{c_{2}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}}$

The video decoder may be configured to filter the extended referencesamples so as to obtain filtered extended reference samples (r(x,−1−i),r(−1−i,y), r(−1−i,−1−i) for i>0) (combined) using one of a 3-tap filter,a 5-tap filter and a 7-tap filter and to use the filtered extendedreference samples for the prediction.

The video decoder may be configured to use a combination of extendedcorner reference samples of the prediction block and of extendedreference samples being arranged in a corner region of reference samples(r(−1−i,−1−i)).

The video decoder may be configured to obtain the combined predictionbased on the determination rule:

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}\frac{\sum_{x_{0} = {- 1}}^{{- 1} - i}{r\left( {x_{0},{{- 1} - i}} \right)}}{i + 1}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}} +}\end{matrix} \\{{{b\left( {x,y} \right)} \cdot {p\left( {x,y} \right)}} + 64}\end{matrix}}{128}$

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and

$\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}$

for i>0 are the combined extended corner reference samples with respectto a boundary of the prediction block and b(x,y) denotes a normalizationfactor.

The video decoder may be configured to obtain the prediction p(x,y)based on an intra-picture prediction. The video decoder may use, forexample, only planar prediction as intra-picture prediction.

The video decoder may be configured, for each decoded video block, todetermine a parameter set identifying the combination of the predictionand the filtered extended reference samples.

The video decoder may be configured to determine the parameter setidentifying the combination of the prediction and the filtered extendedreference samples using a look-up table containing sets for differentblock sizes of the prediction block.

When the reference samples are filtered, it is possible to combine theprediction that uses the filtered samples with the unfiltered referencesamples based on a position of the respective samples o as to obtain aposition depending prediction combination. Let, according to an exampleembodiment, p(x, y) be the prediction using filtered reference samplesand r(x, y) be the unfiltered reference samples. The combined predictionp_(c) (x, y) can be calculated as follows:

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {x,{- 1}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {{- 1},{- 1}} \right)}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{- 1},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{- 1},{- 1}} \right)}} +}\end{matrix} \\{{{b\left( {x,y} \right)} \cdot {p\left( {x,y} \right)}} + 64}\end{matrix}}{128}$

The coefficients c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) are storedprediction weights that are scaled by position dependent terms whered_(x)=1 for blocks with width smaller than or equal to 16 and d_(x)=2for blocks with width larger than 16, d_(y), =1 for blocks with heightsmaller than or equal to 16 and d_(y), =2 for blocks with height largerthan 16. The normalization factor b(x, y) may be derived as follows:

${b\left( {x,y} \right)} = {{128} - \frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}} + \frac{c_{2}^{(v)}}{2^{{y/d_{y}}}} - \frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}} + \frac{c_{2}^{(h)}}{2^{{x/d_{x}}}}}$

As already described in connection with the reference sample filtering,the reference sample filtering for this combination can be differentfrom the filtering for regular predictions. For example, one of e.g.,three or less or more pre-defined low pass filters can be used to smooththe boundary samples. The three pre-defined low-pass filters can includeone 3-tap, one 5-tap and one 7-tap filter. In order to adapt thesmoothing to the content, the selection of smoothing filter can be basedon the block size and the intra prediction mode. Defining h_(k) as theimpulse response of a filter k, and an additional stored weightingparameter a, the filtered reference r′ is computed from the non-filteredreference r as follows where “*” represents convolution:

r′=αr+(1−α)(h _(k) *r)

Accounting again for different characteristics of different block sizes,one fixed set of prediction parameters (c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂^(h), α and filter index k) can be defined per block size.

This known combination for nearest reference samples can be improved byembodiments by using extended reference samples for the filtered andunfiltered reference samples. In the following, a prediction combinationaccording to an embodiment and with extended reference samples is shownwhere the nearest corner sample r(−1,−1) is replaced by the extendedcorner sample r(−1−i, −1−i) as follows.

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} +}\end{matrix} \\{{{b\left( {x,y} \right)} \cdot {p\left( {x,y} \right)}} + 64}\end{matrix}}{128}$

Another embodiment for extended reference samples refers to replace thenearest corner sample r(−1,−1) with the closed extended vertical cornersample r(−1−i, −1) and horizontal corner sample r(−1, −1−i) as follows:

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {{- 1},{{- 1} - i}} \right)}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}\frac{r\left( {{{- 1} - i},{- 1}} \right)}{i + 1}} +}\end{matrix} \\{{{b\left( {x,y} \right)} \cdot {p\left( {x,y} \right)}} + 64}\end{matrix}}{128}$

Another embodiment for extended reference samples defines to replace thenearest corner sample r(−1,−1) with an average of the horizontal andvertical corner samples (both including the corner sample) as follows.

${p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}\frac{\sum_{x_{0} = {- 1}}^{{- 1} - i}{r\left( {x_{0},{{- 1} - i}} \right)}}{i + 1}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}} +}\end{matrix} \\{{{b\left( {x,y} \right)} \cdot {p\left( {x,y} \right)}} + 64}\end{matrix}}{128}$

In one embodiment, the prediction p(x, y) to be combined is a planarprediction. In another embodiment, the combination can be applied toother intra-picture predictions such as DC or angular as well.

Alternatively or in addition, to combine a prediction with samples,different extended prediction modes may be combined.

A video encoder according to an embodiment such as video encoder 1000may be configured to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, for theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and/or a plurality of extendedreference samples, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples;to determine a first prediction for the prediction block using a firstprediction mode of a set of prediction modes, the first set ofprediction modes comprising prediction modes using the plurality ofnearest reference samples in absence of the extended reference samples;and to determine a second prediction for the prediction block using asecond prediction mode of a second set of prediction modes, the secondset of prediction modes comprising a subset of the prediction modes ofthe first set, the subset being associated with the plurality ofextended reference samples. The video encoder may be configured toweightedly (w₀; w_(i)) combine the first prediction (p₀(x,y)) and thesecond prediction (p_(i)(x,y)) so as to obtain a combined prediction(p(x,y)) as prediction for the prediction block in the coding data.

The video encoder may be configured to use the first prediction and thesecond prediction according to a predefined combination being a portionof possible combinations of enabled first prediction modes and enabledsecond prediction modes.

The video encoder may be configured to signal either the firstprediction mode or the second prediction mode whilst not signaling theother prediction mode. For example, the first mode may be derived fromthe parameter i based on additional implicit information such asspecific prediction modes that only may be used in connection with aspecific index i or index m.

The video encoder may be configured to exclusively use, as an examplefor such implicit information, a planar prediction mode as one of thefirst prediction mode and the second prediction mode.

The video encoder may be configured to adapt a first weight applied tothe first prediction in the combined prediction and a second weightapplied to the second prediction in the combined prediction based on ablock size of the prediction block; and/or to adapt the first weightbased on the first prediction mode or the second weight based on thesecond prediction mode.

The video encoder may be configured to adapt a first weight applied tothe first prediction in the combined prediction and a second weightapplied to the second prediction in the combined prediction based on aposition and/or distance in the prediction block.

The video encoder may be configured to adapt the first weight and thesecond weight based on the determination rule

p(x,y)=w ₀(x,y)p ₀(x,y)+w _(i)(x,y)p _(i)(x,y)

wherein w₀(x,y) is the first weight based on the position x,y in theprediction block, w_(i) is the second weight based on the position x,yin the prediction block, p₀(x,y) is the first prediction for theposition x,y and p_(i)(x,y) is the second prediction for the positionx,y, and i indicates the extended reference samples to be used for thesecond prediction.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for decoding aprediction block of a picture, a plurality of nearest reference samplesof the picture directly neighboring the prediction block and/or aplurality of extended reference samples, each extended reference sampleof the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples;

determine a first prediction for the prediction block using a firstprediction mode of a set of prediction modes, the first set ofprediction modes comprising prediction modes using the plurality ofnearest reference samples in absence of the extended reference samples;and to determine a second prediction for the prediction block using asecond prediction mode of a second set of prediction modes, the secondset of prediction modes comprising a subset of the prediction modes ofthe first set, the subset being associated with the plurality ofextended reference samples. The video decoder may be configured toweightedly (w₀; w_(i)) combine the first prediction (p₀(x,y)) and thesecond prediction (p_(i)(x,y)) so as to obtain a combined prediction(p(x,y)) as prediction for the prediction block in the coding data.

The video decoder may be configured to use the first prediction and thesecond prediction according to a predefined combination being a portionof possible combinations of enabled first prediction modes and enabledsecond prediction modes. This allows to obtain a low load of signaling.

The video decoder may be configured to receive a signal indicating thesecond prediction mode whilst not receiving a signal indicating thefirst prediction mode and to derive the first prediction mode from thesecond prediction mode or a parameter information (i).

The video decoder may be configured to exclusively use a planarprediction mode as one of the first prediction mode and the secondprediction mode.

The video decoder may be configured to adapt a first weight applied tothe first prediction in the combined prediction and a second weightapplied to the second prediction in the combined prediction based on ablock size of the prediction block; and/or to adapt the first weightbased on the first prediction mode or the second weight based on thesecond prediction mode.

The video decoder may be configured to adapt a first weight applied tothe first prediction in the combined prediction and a second weightapplied to the second prediction in the combined prediction based on aposition and/or distance in the prediction block.

The video decoder may be configured to adapt the first weight and thesecond weight based on the determination rule

p(x,y)=w ₀(x,y)p ₀(x,y)+w _(i)(x,y)p _(i)(x,y)

wherein w₀(x,y) is the first weight based on the position x,y in theprediction block, w_(i) is the second weight based on the position x,yin the prediction block, p₀(x,y) is the first prediction for theposition x,y and p_(i)(x,y) is the second prediction for the positionx,y, and i indicates the extended reference samples to be used for thesecond prediction. For a varying position x,y in the prediction block,the extended reference samples i may comprise varying distances.Alternatively or in addition, different sets of predefined extendedreference samples, indicated by the area index i and/or by mode m maycomprise different distances to the prediction block.

When using different reference sample areas, it is possible to combinethe prediction p_(o) (x, y) using the nearest reference samples modeswith a prediction p_(i)(x, y) using the extended reference samples i asfollows:

p(x,y)=w ₀ p ₀(x,y)+w _(i) p _(i)(x,y)

One known way to combine the predictions is with fixed weights and usingthe same prediction mode for both predictions. This eliminates the needto signal a second prediction mode.

An embodiment to loosen this tight restriction defines to allow onlyspecific combinations of modes. This still involves signaling of thesecond mode but it limits the number of mode to signal compared to thefirst mode. More details on prediction mode signaling are given inconnection with mode and reference signaling. One promising combinationaccording to an embodiment is to use only planar as second mode so thatan additional signaling of intra modes is obsolete. For example, onecould use p_(i)(x, y) with an arbitrary intra mode as first part of theweighted sum and the second part is generated by using the nearestreference samples and planar mode. Another possibility is to switch theorder, i.e. the planar mode is used for the extended reference samples.

In order to adapt the weighting to the prediction size and mode, theweights w can be specified separately per block size as well as perintra prediction mode. Furthermore, the weights can be signaled on asequence, picture or slice level to be able to adapt the combination tothe video content. Another embodiment is to weight the differentreference sample predictions differently for different areas inside theprediction block. This may result in position-dependent weights w(x, y)as follows:

p(x,y)=w ₀(x,y)p ₀(x,y)+w _(i)(x,y)p _(i)(x,y)

In case of using one prediction and extended reference samples, it isstate of the art to signal the prediction mode and the reference areaindex i that is used, i.e., to perform mode and reference areasignaling. In the following, embodiments to prediction mode coding incase of using one and/or more predictions are presented followed byembodiments to extended reference area index coding.

A video encoder according to an embodiment such as video encoder 1000may be configured 1000 to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, for theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and/or a plurality of extendedreference samples, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples;to use a prediction mode being one of a first set of prediction modesfor predicting the prediction block using the nearest reference samples,for example to use only the nearest sample or at least in absence ofextended reference samples; or being one of a second set of predictionmodes for predicting the prediction block using the extended referencesamples; wherein the second set of prediction modes is a subset of thefirst set of prediction modes, the second subset may be determined bythe encoder; wherein a subset may also include a coincidence of bothsets. The video encoder may be configured to signal a mode information(m) indicating the prediction mode used for predicting the predictionblock; and to afterwards signal a parameter information (i) indicating asubset of the extended reference samples used for the prediction mode ifthe prediction mode is contained in the second set of prediction modes;and to skip signaling the parameter information when the used predictionmode is not contained in the second set of prediction modes, therebyallowing the conclusion that the parameter i has a predefined value suchas 0.

The video encoder may be configured to skip signaling the parameterinformation, when the mode information indicates a DC mode or a planarmode.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for decoding aprediction block of a picture, a plurality of nearest reference samplesof the picture directly neighboring the prediction block and/or aplurality of extended reference samples, each extended reference sampleof the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples; to use a prediction mode being one of afirst set of prediction modes for predicting the prediction block usingthe nearest reference samples, for example to use only the nearestsample or at least in absence of extended reference samples; or beingone of a second set of prediction modes for predicting the predictionblock using the extended reference samples. The second set of predictionmodes is a subset of the first set of prediction modes and may bedetermined and/or signaled by the encoder. Being a subset may include acoincidence of both sets. The video encoder may be configured to receivea mode information (m) indicating the prediction mode used forpredicting the prediction block; and afterwards receive a parameterinformation (i) indicating a subset of the extended reference samplesused for the prediction mode thereby indicating that the prediction modeis contained in the second set of prediction modes; and to determinethat the used prediction mode is not contained in the second set ofprediction modes when not receiving the parameter information and todetermine a use of the nearest reference samples for the prediction.

The video decoder may be configured to determine the mode information asindicating a use of a DC mode or a planar mode when not receiving theparameter information.

When the set of allowed intra prediction modes for extended referencesamples is restricted, i.e. a subset of the allowed intra predictionmodes for nearest reference samples, there are two different ways tosignal the mode m and the index i, e.g., when the subset is referred toas restricted prediction modes for the extended reference samples:

-   -   1. Signal mode m before index i so that the index signaling can        depend on the mode m as follows:        -   a. If the mode m is not in the set of allowed modes for            extended reference samples, the signaling of the index i is            skipped and the prediction mode m is applied to the nearest            reference samples (i=0)        -   b. Otherwise, i is signaled and the prediction mode m is            applied to the reference samples indicated by i.    -   2. Signal index i before the mode m so that the mode signaling        can depend in the index i as follows:        -   a. If i indicates to use extended reference samples (i>0),            the set of allowed modes m to be signaled is equal to the            restricted one.        -   b. Otherwise (i=0), the set of allowed modes m to be            signaled is equal to the unrestricted set of modes    -   For example, if the mode m is signaled using most probable mode        (MPM) coding with an index to the MPM list, the modes that are        not in the allowed set of modes are not included in the MPM        list.

I.e., according to a second option that may be implemented alternativelyor in addition, a video encoder according to an embodiment such as videoencoder 1000 may be configured to encode, by block based predictiveencoding, pictures of a video into coding data, wherein the block basedpredictive encoding comprises an intra-picture prediction; to use, forthe intra-picture prediction, for encoding a prediction block of apicture, a plurality of reference samples comprising nearest referencesamples of the picture directly neighboring the prediction block and aplurality of extended reference samples, each extended reference sampleof the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples; to use a prediction mode being one of afirst set of prediction modes for predicting the prediction block usingthe nearest reference samples; or being one of a second set ofprediction modes for predicting the prediction block using the extendedreference samples; wherein the second set of prediction modes is asubset of the first set of prediction modes; to signal a parameterinformation (i) indicating a subset of the plurality of referencesamples used for the prediction mode, the subset of the plurality ofreference samples comprising nearest reference samples only or extendedreference samples; and to afterwards signal a mode information (m)indicating the prediction mode used for predicting the prediction block,wherein the mode information indicates a prediction mode from a subsetof modes, the subset being restricted to a set of allowed predictionmodes according to the parameter information (i).

For both options, the video decoder be adapted such that the extendedreference samples in modes contained in the second set of predictionmodes are used in addition to the nearest reference samples.

Further, the video encoder may be adapted such that the first set ofprediction modes describes prediction modes allowed for being used withthe nearest reference samples, wherein the second set of predictionmodes describes prediction modes of the first set of prediction modesbeing also allowed for being used with the extended reference samples.

A range of values of the parameter information i.e., a domain of valuesthat may be represented by the area index i, may cover a use of thenearest reference values only and a use of different subsets of extendedreference values. As described in connection with FIG. 11, i mayrepresent a use of nearest reference values only (i=0) a specific set ofextended reference values or a combination of sets (e.g., lines and/orcolumns or distances) of extended reference values.

According to an embodiment, different portions of extended referencesamples comprise a different distance to the prediction block.

The video encoder may be configured to set the parameter information toone of a predefined number of values, the value indicating a number anda distance of reference samples used for the prediction mode.

The video encoder may be configured to determine the first set ofprediction modes and/or the second set of prediction modes based on amost probable mode coding.

A corresponding decoder of the second option is configured to decode, byblock based predictive decoding, pictures coded in coding data into avideo, wherein the block based predictive decoding comprises anintra-picture prediction; to use, for the intra-picture prediction, fordecoding a prediction block of a picture, a plurality of referencesamples comprising nearest reference samples of the picture directlyneighboring the prediction block and a plurality of extended referencesamples, each extended reference sample of the plurality of extendedreference samples separated from the prediction block at least by onenearest reference sample of the plurality of reference samples; to use aprediction mode being one of a first set of prediction modes forpredicting the prediction block using the nearest reference samples; orbeing one of a second set of prediction modes for predicting theprediction block using the extended reference samples; wherein thesecond set of prediction modes is a subset of the first set ofprediction modes; to receive a parameter information (i) indicating asubset of the plurality of reference samples used for the predictionmode, the subset of the plurality of reference samples comprisingnearest reference samples only or an extended reference samples; and toafterwards receive a mode information (m) indicating the prediction modeused for predicting the prediction block, wherein the mode informationindicates a prediction mode from a subset of modes, the subset beingrestricted to a set of allowed prediction modes according to theparameter information (i).

A decoder according to the first option and/or the second option may beadapted such that the extended reference samples in modes contained inthe second set of prediction modes are used in addition to the nearestreference samples, for example by combining prediction and samplesand/or combining predictions.

The first set of prediction modes may describe prediction modes allowedfor being used with the nearest reference samples, wherein the secondset of prediction modes may describe prediction modes of the first setof prediction modes being also allowed for being used with the extendedreference samples.

As described for the encoder, a range of values of the parameterinformation covers a use of the nearest reference values only and a useof different subsets of extended reference values.

Different portions of extended reference samples may comprise adifferent distance to the prediction block.

The video decoder may be configured to set the parameter information toone of a predefined number of values, the value indicating a number anda distance of reference samples used for the prediction mode.

The video decoder may be configured to determine the first set ofprediction modes and/or the second set of prediction modes based on amost probable mode (MPM) coding, i.e., it may generate a respectivelist, wherein the list may be adapted so as to contain such modes onlythat are allowed for the respective samples to be used.

Alternatively or in addition, embodiments relating to combiningpredictions from nearest and extended reference samples may beimplemented.

A video encoder according to an embodiment such as video encoder 1000may be configured to encode, by block based predictive encoding,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, for theintra-picture prediction, for encoding a prediction block of a picture,a plurality of nearest reference samples of the picture directlyneighboring the prediction block and/or a plurality of extendedreference samples, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples;to determine a first prediction for the prediction block using a firstprediction mode of a set of prediction modes, the first set ofprediction modes comprising prediction modes using the plurality ofnearest reference samples in absence of the extended reference samples;to determine a second prediction for the prediction block using a secondprediction mode of a second set of prediction modes, the second set ofprediction modes comprising a subset of the prediction modes of thefirst set being associated with the plurality of extended referencesamples, and to combine the first prediction and the second predictionso as to obtain a combined prediction as prediction for the predictionblock in the coding data.

The prediction block may be a first prediction block, wherein the videoencoder may be configured to predict a second prediction block of thevideo using a plurality of nearest reference samples associated with thesecond prediction block in absence of a plurality of extended referencesamples associated with the second prediction block. The video encodermay be configured to signal a combining information such as a bipredflag indicating that the prediction in the coding data is based on acombination of predictions or is based on a prediction using theplurality of extended reference samples in absence of the plurality ofnearest reference samples.

The video encoder may be configured to use the first prediction mode asa predefined prediction mode.

The video encoder may be configured to select the first prediction modeas being a same mode as the second prediction mode and using the nearestreference samples in absence of the extended reference samples; or touse the first prediction mode as preset prediction mode such as a planarprediction mode.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for decoding aprediction block of a picture, a plurality of nearest reference samplesof the picture directly neighboring the prediction block and/or aplurality of extended reference samples, each extended reference sampleof the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples; to determine a first prediction for theprediction block using a first prediction mode of a set of predictionmodes, the first set of prediction modes comprising prediction modesusing the plurality of nearest reference samples in absence of theextended reference samples; and to determine a second prediction for theprediction block using a second prediction mode of a second set ofprediction modes, the second set of prediction modes comprising a subsetof the prediction modes of the first set being associated with theplurality of extended reference samples. The video decoder may beconfigured to combine the first prediction and the second prediction soas to obtain a combined prediction as prediction for the predictionblock in the coding data.

The prediction block may be a first prediction block, wherein the videodecoder may be configured to predict a second prediction block of thevideo using a plurality of nearest reference samples associated with thesecond prediction block in absence of a plurality of extended referencesamples associated with the second prediction block. The video decodermay further be configured to receive the combining informationindicating that the prediction in the coding data is based on acombination of predictions or is based on a prediction using theplurality of extended reference samples in absence of the plurality ofnearest reference samples and do decode the coding data accordingly.

The video decoder may be configured to use the first prediction mode asa predefined prediction mode.

The video decoder may be configured to select the first prediction modeas being a same mode as the second prediction mode and using the nearestreference samples in absence of the extended reference samples; or touse the first prediction mode as preset prediction mode such as theplanar mode.

If the reference area index i indicates the use of extended referencesamples (i>0), a respective information such as binary information or aflag, referred to hereinafter as Bi-Prediction flag (bipred flag) may beused to signal whether the prediction using extended reference samplesis combined with a prediction using nearest reference samples.

If the bipred flag indicates a combination of predictions from nearest(i=0) and extended reference samples (i>0), the mode for the extendedreference samples m_(i) is signaled either before the reference areaindex i or after as described herein. The mode for the nearest referencesample prediction m₀ is fixed, e.g. set to a specific mode like planaror set to the same mode as for the extended reference samples.

As will be described in the following, a video encoder according to anembodiment may be configured to encode, by block based predictiveencoding, pictures of a video into coding data, wherein the block basedpredictive encoding comprises an intra-picture prediction; to use, inthe intra-picture prediction, for encoding a prediction block of apicture, a plurality of extended reference samples of the picture, eachextended reference sample of the plurality of extended reference samplesseparated from the prediction block at least by one nearest referencesample of the plurality of reference samples, directly neighboring theprediction block; and to use the plurality of extended reference samplesaccording to a predefined set of pluralities of extended referencesamples, i.e., a list of area indices may be generated and/or used, thelist indicating specific subsets of reference samples, such as nearestreference samples only, at least one distance of extended referencesamples and/or a combination of different distances of extendedreference samples.

The video encoder may be configured to determine the predefined set ofpluralities of extended reference samples such that pluralities in theset differ with respect to each other by a number or combination oflines and/or rows of samples of the picture to be used as referencesamples.

The video encoder may be configured to determine the predefined set ofpluralities of extended reference samples based on a block size of theprediction block and/or a prediction mode used to predict the predictionblock.

The video encoder may be configured to determine the set of pluralitiesof extended reference samples for a block size of the prediction blockbeing at least a predefined threshold and to skip signaling the set ofpluralities of extended reference samples when the block size is belowthe predefined threshold value.

The predefined threshold may be a predefined number of samples along awidth or height of the prediction block and/or a predefined aspect ratioof the prediction block along the width and the height.

The predefined number of samples may be of any number but isadvantageously 8. Alternatively or in addition, the aspect ratio maygreater than 1/4 and less than 4, probably based on the number of 8samples defining one quotient of the aspect ratio.

The video encoder may be configured to predict the prediction block as afirst prediction block using the plurality of extended reference samplesand to predict a second prediction block (that may be part of the sameor a different picture) not using extended reference samples, whereinthe video encoder is configured to signal a predefined set ofpluralities of extended reference samples associated with the firstprediction block and to not signal a predefined set of extendedreference samples in associated with the second prediction block. Thepredefined set may be indicated by the reference area index i, forexample.

The video encoder may be configured to signal, for each predictionblock, information indicating one of a specific plurality of a set ofpluralities of extended reference samples and a use of nearest referencesamples only before information indicating the intra-picture predictionmode.

The video encoder may be configured to signal the information indicatingthe intra-picture prediction so as to thereby indicate prediction modesthat are in accordance with the indicated specific plurality of the setof pluralities of extended reference samples or in accordance with theindicated use of nearest reference samples, only.

A corresponding video decoder may be configured to decode, by blockbased predictive decoding, pictures coded in coding data into a video,wherein the block based predictive decoding comprises an intra-pictureprediction; to use, in the intra-picture prediction, for decoding aprediction block of a picture, a plurality of extended reference samplesof the picture, each extended reference sample of the plurality ofextended reference samples separated from the prediction block at leastby one nearest reference sample of the plurality of reference samples,directly neighboring the prediction block; and to use the plurality ofextended reference samples according to the predefined set ofpluralities of extended reference samples.

The video decoder may be configured to determine the predefined set ofpluralities of extended reference samples such that pluralities in theset differ with respect to each other by a number or combination oflines and/or rows of samples of the picture to be used as referencesamples.

The video decoder may be configured to determine the predefined set ofpluralities of extended reference samples based on a block size of theprediction block and/or a prediction mode used to predict the predictionblock.

The video decoder may be configured to determine the set of pluralitiesof extended reference samples for a block size of the prediction blockbeing at least a predefined threshold and to skip using the set ofpluralities of extended reference samples when the block size is belowthe predefined threshold value.

For example, the signaling of the set (which may use a parameterinformation i or similar syntax) may be skipped if the top-left sampleof the current block at location (x0,y0) is located in the first rowinside a coding tree block (CTB). A CTB may be considered as the basicprocessing unit into which a picture is partitioned and which is theroot of further block sub-partitioning.

This may be done by checking whether the vertical y-coordinate y0 is nota multiple of the CTB size. E.g., when the CTB size is 64 luma samples,in the first CTB row, the above blocks inside a CTB have y0=0, in thesecond CTB row, they have y0=64 and so on. So for all blocks inside aCTB, that are located at the upper boundary of this CTB (which can bechecked e.g. by a modulo operation as follows: y0% CtbSizeY==0), thesignaling of the parameter i or similar syntax may be skipped.

The predefined threshold may accordingly be the predefined number ofsamples along a width or height of the prediction block and/or apredefined aspect ratio of the prediction block along the width and theheight.

Thus, the predefined number of samples may be 8 and/or the aspect ratiomay be needed to be greater than 1/4 and at less than 4.

The video decoder may be configured to predict the prediction block as afirst prediction block using the plurality of extended reference samplesand to predict a second prediction block not using extended referencesamples, wherein the video decoder is configured to receive informationindicating a predefined set of pluralities of extended reference samplesassociated with the first prediction block, for example, using the areaindex i, and to determine a predefined set of extended reference samplesin associated with the second prediction block in absence of arespective signal.

The video decoder may be configured to receive, for each predictionblock, information indicating a one of a specific plurality of a set ofpluralities of extended reference samples and a use of nearest referencesamples only before information indicating the intra-picture predictionmode.

The video decoder may be configured to receive the informationindicating the intra-picture prediction so as to thereby indicateprediction modes that are in accordance with the indicated specificplurality of the set of pluralities of extended reference samples or inaccordance with the indicated use of nearest reference samples, only.

The reference area index can be changed per block and hence, the indexcan be transmitted in the bitstream for every prediction block itapplies to. Embodiments relate to an extended reference sample areasignaling so as to allow the decoder to use the correct samples. Thearea may correspond to the parameter i indicating the extended referencesamples or nearest reference samples. In order to trade-off signalingand the use of further distanced extended reference samples, apredetermined set of extended reference sample lines can be used. Forexample, only two additional extended reference lines can be used whichare the lines with index 1 and 3. The set according to the embodimentmay be I={0,1,3} with |I|=3. This allows the reference sample area to beextended up to three additional lines but only need signaling for two.The set could also be extended to four lines, e.g. I={0,1,3,4} and onlythe first MaxNumRefAreaIdx elements are used while MaxNumRefAreaIdx canbe fixed or signaled on a sequence, picture or slice level. The index ninto a set I can be signaled in the bitstream using entropy coding and atruncated unary code as shown in the table illustrated in FIG. 11showing an example truncated unary code for a specific set of referenceareas for MaxNumRefAreaIdx equal to 3 and 4.

In order to account for different spatial characteristics of differentblock sizes, the set of reference sample lines can also depend on theprediction block size and/or intra prediction mode. In anotherembodiment, the set contains only one additional line with index 2 forsmall blocks and two lines with index 1 and 3 lines larger blocks. Anembodiment for an intra-prediction mode dependent set selection is tohave a different set of reference sample lines for prediction directionsbetween the horizontal and the vertical directions.

By selecting an empty set for smaller block sizes which does not needsignaling, the signaling of the reference area index could also berestricted to larger block sizes. This may basically disable the use ofextended reference samples for smaller block sizes. In one embodimentthe use of extended reference samples could be restricted to a blockwith both width W and height H being larger or equal to 8. In additionto that, blocks with one side being smaller than or equal to one fourthof the other side could also be excluded from using extended referencesamples, e.g. 32×8 blocks or, based on the mentioned symmetry, 8×32blocks. FIG. 12a and FIG. 12b illustrate this embodiment where someblock sizes are already excluded for intra-picture prediction (FIG. 12a) in general as indicated by reference sign 1102 and blocks shadedaccordingly. In this embodiment it is assumed that intra-pictureprediction slices and inter-picture prediction slices allow differentblock size combinations. Samples 1104 and blocks shaded accordingly arenot allowed for extended reference samples, i.e., for i>0. FIG. 12a andFIG. 12b show example restrictions for extended reference samples forintra-picture prediction slices and inter-picture prediction slices. Asmay be seen, allowance or restriction of a block dependent from a blocksize, in particular from an aspect ratio of the block may be symmetricfor quotients W/H and H/W.

In case there exist other intra-prediction modes that do not useextended reference samples, the reference area index is only signaled ifa prediction mode that uses extended reference samples is signaled.Another way may be to signal the reference area index before all otherintra mode information is signaled. In case the reference area index iindicates extended references samples (i>0), the signaling of modeinformation that does not use extended reference samples (e.g. templatematching or trained predictors) can be skipped. This can also skipsignaling information of specific transforms that do not apply toprediction residuals for predictions that use extended referencesamples.

In the following reference is made to embodiments referring toconsiderations for parallel coding.

A video encoder according to an embodiment may be configured to encode,by block based predictive encoding a plurality of prediction blocks,pictures of a video into coding data, wherein the block based predictiveencoding comprises an intra-picture prediction; to use, for theintra-picture prediction, for encoding a prediction block of theplurality of prediction blocks, a plurality of extended referencesamples of the picture, each extended reference sample of the pluralityof extended reference samples separated from the prediction block atleast by one nearest reference sample of the plurality of referencesamples, directly neighboring the prediction block; wherein the videoencoder may be configured to determine the extended reference samples soas to be at least partially a part of an adjacent prediction block ofthe plurality of prediction blocks, and to determine that the adjacentprediction block has not yet been predicted; and to signal informationindicating the extended prediction samples associated to the predictionblock and arranged in the adjacent prediction block as unavailablesamples.

The video encoder may be configured to encode the pictures by parallelencoding lines of blocks according to a wavefront approach, and topredict the prediction block based on an angular prediction, wherein thevideo encoder is configured to determine the extended reference samplesto be used for predicting the prediction block so as to be arranged inalready predicted blocks of the picture. According to the wavefrontapproach a coding or decoding of a second line may trail a decoding of afirst line, e.g., separated by one block. For example, in a verticalangular mode of 45° at most one block above right may be coded decodedwhen starting from the second line.

The video encoder may be configured to signal the extended predictionsamples associated to the prediction block and arranged in the adjacentprediction block variantly as unavailable samples or available sampleson a sequence level, i.e., a sequence of pictures, a picture level or aslice level, the slice being a part of a picture.

The video encoder may be configured to signal the information indicatingthe extended prediction samples associated to the prediction block andarranged in the adjacent prediction block as unavailable samplestogether with information indicating a parallel coding of the picture.

A corresponding decoder may be configured to decode, by block basedpredictive decoding, pictures coded in coding data into a video, whereinfor each picture a plurality of prediction blocks is decoded, whereinthe block based predictive decoding comprises an intra-pictureprediction; to use, for the intra-picture prediction, for decoding aprediction block of the plurality of prediction blocks, a plurality ofextended reference samples of the picture, each extended referencesample of the plurality of extended reference samples separated from theprediction block at least by one nearest reference sample of theplurality of reference samples, directly neighboring the predictionblock; wherein the video decoder is configured to determine the extendedreference samples so as to be at least partially a part of an adjacentprediction block of the plurality of prediction blocks, and to determinethat the adjacent prediction block has not yet been predicted; and toreceive information indicating the extended prediction samplesassociated to the prediction block and arranged in the adjacentprediction block as unavailable samples.

The video decoder may be configured to decode the pictures by paralleldecoding lines of blocks according to a wavefront approach, and topredict the prediction block based on an angular prediction, wherein thevideo decoder is configured to determine the extended reference samplesto be used for predicting the prediction block so as to be arranged inalready predicted blocks of the picture.

The video decoder may be configured to receive information indicatingthe extended prediction samples associated to the prediction block andarranged in the adjacent prediction block variantly as unavailablesamples or available samples on a sequence level, a picture level or aslice level.

The video decoder may be configured to receive the informationindicating the extended prediction samples associated to the predictionblock and arranged in the adjacent prediction block as unavailablesamples together with information indicating a parallel decoding of thepicture.

In angular intra-picture prediction, reference samples are copied intothe current prediction area along a specified direction. In case thatthis direction points to the top right, the needed reference sample areaalso shifts to the right the larger the distance to the prediction areaboundary gets. FIG. 13 shows an embodiment of vertical angularprediction with an angle of 45 degree of an W×H prediction block. It canbe seen that nearest reference sample area (blue) extends H samples tothe top right of the current W×H block. Extending the prediction to moredistant reference sample areas, the extended reference samples (green)extend H+1, H+2, . . . samples to the top right of the current W×Hblock.

When for example square Coding Tree Units (CTU) are used as basicprocessing unit, the maximum intra prediction block size can be equal tothe maximum block size, i.e. the CTU block size N×N. FIG. 14a and FIG.14b illustrate the embodiment from FIG. 13 with the W×H prediction blockbeing equal to the N×N CTU block size. Correspondingly, the extendedreference samples 10641 and/or 10642 span over the top right CTU (CTU 2)and reach at least one sample into the next CTU (CTU 3). I.e., a portionof the extended reference samples 10641 and/or 10642 of the 45° verticalangular prediction may be arranged in unprocessed CTU 3. Those samplesmay be unavailable if CTU3 and CTU5 are processed in parallel.

FIG. 14a and FIG. 14b show an example of needed nearest referencesamples 1062 and extended reference samples 1064 in case of diagonalvertical intra-picture prediction.

In FIG. 14b , two CTU lines can be seen. When encoding the two lines inparallel using a wavefront-like approach, the encoding of the second CTUline can start with CTU 5 once CTU 2 is encoded and the encoding of CTU3 starts. In this case, 45-degree vertical angular prediction withextended reference samples cannot be used in CTU 5 since some referencesamples 1104 are located inside CTU 3. The following approaches cansolve this problem:

-   -   1. Mark extended reference inside a next basic processing area        as unavailable as described in connection with present        embodiments. That way they can be treated like other unavailable        reference samples, e.g. at picture, slice or tile boundaries or        when constrained intra prediction is used that disallows using        samples from inter-picture predicted areas as reference for        intra-picture prediction areas.    -   2. Allow using extended reference samples only for areas and        intra-picture prediction modes so the reference samples do not        extend to more than one basic processing unit to the top right        of the current area.

Both approaches can be made switchable by a high-level flag on asequence, picture or slice level. That way, the encoder can signal thedecoder to apply the restrictions in case it is needed by the parallelprocessing scheme of the encoder. In case that it is not needed, theencoder can signal the decoder that no restrictions apply.

Another way is to combine the signaling for both restriction with thesignaling of parallel encoding schemes. For example, when wavefrontparallel processing is enabled and signaled in the bitstream, therestriction on extended reference samples also apply.

In the following, some advantageous embodiments are described.

1. In one embodiment, intra prediction is using two additional referencelines with reference sample area index i=1 and i=3 (see FIG. 3). Forthese extended reference samples lines, only angular prediction asdescribed herein are allowed. The signaling of the reference sample areaindex i is performed as described in connection with FIG. 11 withMaxNumRefAreaIdx=3 and signaled before signaling the intra predictionmode. When the reference area index is not equal to 0, i.e. extendedreference lines are used, DC and planar intra prediction modes are notused. In order to avoid unnecessary signaling, DC and planar modes areexcluded from the intra prediction mode signalization. The intraprediction mode can be coded using an index to a list of most probablemodes (MPM). The MPM list contains a fixed number of prediction modecandidates which are derived from neighboring blocks. When theneighboring blocks are coded using the nearest reference lines (i=0),they can use DC or planar mode and hence, the MPM list derivationprocess is modified to not include DC and planar mode. If removed, DCand planar modes can be replaced by horizontal, vertical and bottom leftdiagonal angular modes to fill up the list (see FIG. 4a to FIG. 4e ).This is done in a way to avoid redundancies, e.g. when the firstcandidate mode derived from a neighboring block is vertical and thesecond candidate mode is DC, the DC mode is not replaced by a verticalmode but by horizontal since it is not in the list yet. Another way toprevent unnecessary signaling of DC and planar mode in case of i>0 is tosignal the reference area index i after the prediction mode andcondition the signaling of i on the prediction mode. If the intraprediction mode is equal to DC or planar, no index i is signaled.However, the previous described method is advantageous over this methodsince this one introduces a parsing dependency in case the intraprediction mode is signaled using an index to an MPM list. In order tobe able to parse i, the intra prediction mode has to be reconstructedwhich needs MPM list derivation. MPM list derivation on the other handrefers to the prediction modes of the neighboring blocks which needs tobe reconstructed before parsing i as well. This undesired parsingdependency is solved by signaling i before the prediction mode andmodify the MPM list derivation accordingly as described above. A videoencoder may be configured to determine a list of most probableprediction modes based on a use of the plurality of nearest referencesamples or the use of the plurality of extended reference samples forthe prediction mode, wherein the video encoder is configured tosubstitute prediction modes restricted for the used reference samples bymodes allowed for the prediction mode. A corresponding video decoder maybe configured to determine a list of most probable prediction modesbased on a use of the plurality of nearest reference samples or the useof the plurality of extended reference samples for the prediction mode,wherein the video decoder is configured to substitute prediction modesrestricted for the used reference samples by modes allowed for theprediction mode

2. In another embodiment, the intra prediction for extended referencesamples is additionally restricted to be applied to luma samples only.I.e., the video encoder may be configured to apply prediction usingextended reference samples to pictures comprising luma information only.Accordingly, the video decoder may be configured to apply predictionusing extended reference samples to pictures comprising luma informationonly.

3. In another embodiment, the extended reference samples (i>0) thatexceed the width and the height of the nearest reference samples (i=0),(see W+H in FIG. 3) are not generated by using already reconstructedsamples (if available) but by padding from the last sample, e.g.r(23,−1−i) for the top-right samples or r(−1−i,23) for the bottom-leftsamples in FIG. 3. This reduces the memory access for the extendedreference sample lines. I.e., the video encoder may be configured togenerate extended reference samples exceeding a width and/or a height ofnearest reference samples along a first and a second image direction bypadding from a closest extended reference sample. Accordingly, the videodecoder may be configured to generate extended reference samplesexceeding a width and/or a height of nearest reference samples along afirst and a second image direction by padding from a closest extendedreference sample.

4. In another embodiment, only every second angular mode can be used forextended reference samples. Consequently, the MPM list derivation ismodified to exclude these modes as well in addition to DC and planarmodes in case of i>0. I.e., the video encoder may be configured topredict the prediction using an angular prediction mode using only asubset of angles from possible angles of the angular prediction mode andto exclude unused angles from signaling encoding information to adecoder. Accordingly, the video decoder may be configured to predict theprediction using an angular prediction mode using only a subset ofangles from possible angles of the angular prediction mode and toexclude unused angles from the prediction.

5. In another embodiment, the number of additional reference samplelines is increased to 3 (see FIG. 11 with MaxNumRefAreaIdx=4). I.e., theextended reference samples may be arranged in at least 2 lines and rowsin addition to nearest reference samples, advantageously at least 3lines and rows. Such configuration may be applied to the video encoderand decoder. The video encoder may be configured to use a specificplurality of a set of pluralities of extended reference samples forpredicting the prediction block, wherein the video encoder is configuredto select the specific plurality from the set of pluralities so as tocomprise a lowest similarity of picture content when compared to aplurality of nearest reference samples extended by the set, i.e., to useassociated reference samples, e.g., having the same reference areaindex. Accordingly, a video decoder may be configured to use a specificplurality of a set of pluralities of extended reference samples forpredicting the prediction block, wherein the video decoder is configuredto select the specific plurality from the set of pluralities so as tocomprise a lowest similarity of picture content when compared to aplurality of nearest reference samples extended by the set.

6. In another embodiment, a flag that indicates whether extendedreference samples are used is signaled instead of the index i. If theflag indicates that extended reference samples are used, the index i(i>0) is derived by calculating the similarity (e.g. using sum ofabsolute differences) between the reference line i>0 and the referenceline i=0. The index i that results in the lowest similarity is chosen.The idea behind that is that the more correlated the extended referencesamples (i>0) and the regular reference samples (i=0) are, the morecorrelated are the resulting predictions and hence there is noadditional benefit from using the extended reference samples inprediction. I.e., the video encoder may be configured to signal a use ofextended reference samples using a flag or other, probably binary,information. Accordingly, the video decoder may be configured to receiveinformation indicating a use of extended reference samples by such aflag.

7. In another embodiment, a secondary transform like a non-separablesecondary transform (NSST) can be applied after a first transform of theintra prediction residual. In case of extended reference sample lines,no secondary transform is performed and all signaling related to NSST isdisabled in case of i>0. I.e., the video encoder may be configured toselectively use the extended reference samples or nearest referencesamples only, wherein the video encoder is configured to transform aresidual obtained by predicting the prediction block using a firsttransformation procedure so as to obtain a first transformation resultand to transform the first transformation result using a secondtransformation procedure so as to obtain a second transformation resultwhen the extended reference samples are unused for predicting theprediction block. This may also affect the signalling of whether asecond transform is used, i.e. if the use of a second transform has tobe signaled, the signaling may be skipped when extended referencesamples are used. The video encoder may be configured to signal a use ofthe secondary transform; or to implicitly signal a non-use of thesecondary transform when indicating a use of the extended referencesamples and to not include information relating to a result of asecondary transform in the coding data.

Accordingly, the video decoder may be configured to selectively use theextended reference samples or nearest reference samples only, whereinthe video decoder is configured to transform a residual obtained bypredicting the prediction block using a first transformation procedureso as to obtain a first transformation result and to transform the firsttransformation result using a second transformation procedure so as toobtain a second transformation result when the extended referencesamples are unused for predicting the prediction block. The videodecoder may video decoder may be configured to receive informationindicating a use of the secondary transform; or to derive a non-use ofthe secondary transform when indicating a use of the extended referencesamples and to not receive information relating to a result of asecondary transform in the coding data.

8. In another embodiment, the prediction that uses extended referencesamples (i>0) is combined with a planar prediction that uses the nearestreference samples (i=0). As outlined in connection with combiningdifferent extended prediction modes, i.e., using extended referencesamples, the weighting can be fixed (e.g. 0.5 and 0.5), block-sizedependent or signaled on a slice, picture or sequence level. In caseextended reference samples are used (i>0), an additional flag indicateswhether the combined prediction is applied or not. I.e., the videoencoder may be configured to. Accordingly, the video decoder may beconfigured to

9. In another embodiment, the signaling of the combined prediction fromabove is omitted to reduce the signalization overhead. Instead, thedecision of whether to apply the combined prediction is derived based onan analysis of the nearest reference samples (i=0). One possibleanalysis could be the flatness of the nearest reference samples. In casethe nearest reference sample signal is flat (no edges), the combinationis applied and if it contains high frequencies and edges, thecombination is not applied. I.e., the video encoder may be configuredto. Accordingly, the video decoder may be configured to

In the following, additional embodiments and aspects of the inventionwill be described which can be used individually or in combination withany of the features and functionalities and details described herein

-   1. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   sequentially determine an availability or unavailability of each        of the plurality of extended reference samples;    -   substitute an extended reference sample being determined as        unavailable by a substitution sample; and    -   use the substitution sample for the intra-picture prediction.-   2. The video encoder of aspect 1, wherein the video encoder is    configured to:    -   determine the availability or unavailability sequentially        according to a sequence;    -   determine the substitution sample as a copy a last extended        reference sample being determined as available in the sequence;        and/or determine the substitution sample as a copy a next        extended reference sample being determined as available in the        sequence.-   3. The video encoder of aspect 2, wherein the video encoder is    configured to:    -   determine the availability or unavailability sequentially        according to a sequence;    -   determine the substitution sample based on a combination of an        extended reference sample being determined as available and        being arranged in the sequence prior to the reference sample        being determined as unavailable and of an extended reference        sample being determined as available and being arranged in the        sequence after the reference sample being determined as        unavailable.-   4. The video encoder of one of previous aspects, wherein the video    encoder is configured to:    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples    -   determine an availability or unavailability of each of the        plurality of extended reference samples;    -   signal a use of the plurality of extended reference samples when        a portion of available extended reference samples of the        plurality of extended reference samples is larger than or equal        a predetermined threshold; and    -   skip signaling the use of the plurality of extended reference        samples when the portion of available extended reference samples        of the plurality of extended reference samples is below the        predetermined threshold.-   5. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   filtering at least a subset of the plurality of extended        reference samples using a bilateral filter or a 3-tap FIR filter        so as to obtain a plurality of filtered extended reference        samples; and    -   use the plurality of filtered extended reference samples for the        intra-picture prediction.-   6. The video encoder of aspect 5, wherein the video encoder is    configured to filter the plurality of extended reference samples    using one of a 3-tap filter, a 5-tap filter and a 7-tap filter.-   7. The video encoder of aspect 6, wherein the video encoder is    configured to predict the prediction block using an angular    prediction mode; wherein the 3-tap filter, a 5-tap filter and a    7-tap filter are configured as bilateral filters, wherein the video    encoder is configured to select to use one of the 3-tap filter, the    5-tap filter and the 7-tap filter based on an angle used for the    angular prediction, the angle arranged between a horizontal or a    vertical direction of the angular prediction mode; and/or wherein    the video encoder is configured to select to use one of the 3-tap    filter, the 5-tap filter and the 7-tap filter based on a block size    of the prediction block.-   8. The video encoder of aspect 7, wherein the video encoder is    configured to select a filter with increasing taps for increasing    angles with from to a horizontal direction or vertical direction    towards a diagonal.-   9. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block,        wherein a plurality of nearest reference samples is arranged        along a first picture direction of the prediction block and        along a second picture direction of the prediction block;    -   map at least a part of the nearest reference samples arranged        along the second direction to extended reference samples being        arranged along the first direction, such that the mapped        reference samples exceed an extension of the prediction block        along the first picture direction; and    -   use the mapped extended reference samples for the prediction.-   10. The video encoder of aspect 9, wherein the video encoder is    configured to map the portion of nearest reference samples according    to a prediction mode used for predicting the prediction block.-   11. The video encoder of aspect 10, wherein the video encoder is    configured to map the portion of nearest reference samples according    to a direction used in the prediction mode for predicting the    prediction block.-   12. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   wherein the video encoder is configured to boundary filtering in        a mode where no extended samples are used; and not to use        boundary filtering when extended samples are used; or    -   wherein the video encoder is configured to boundary filtering at        least a subset of the plurality of nearest reference samples and        not using boundary filtering for the extended samples.-   13. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   determining, in the intra-picture prediction, for encoding a        prediction block of a picture, a plurality of nearest reference        samples of the picture directly neighboring the prediction block        and a plurality of extended reference samples, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples;    -   determining a prediction for the prediction block using the        extended reference samples;    -   filtering the extended reference samples so as to obtain a        plurality of filtered extended reference samples; and    -   combining the prediction and the filtered extended reference        samples so as to obtain a combined prediction for the prediction        block.-   14. The video encoder of aspect 13, wherein the video encoder is    configured to combine the prediction and extended reference samples    being arranged in a major diagonal or minor diagonal of samples with    respect to the prediction block.-   15. The video encoder of aspect 13 or 14, wherein the video encoder    is configured to combine the prediction and the extended reference    samples based on the determination rule:

$\mspace{20mu} {{p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} +}\end{matrix} \\{{b\left( {x,y} \right)} \cdot {p\left( {x,\text{?}} \right.}}\end{matrix}}{128}}$ ?indicates text missing or illegible when filed

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and r(−1−i,−1−i) for i>0 is an extended cornerreference sample of the plurality of extended reference samples withrespect to a boundary of the prediction block and b(x,y) denotes anormalization factor.

-   16. The video encoder of aspect 15, wherein the normalization factor    is determined based on the determination rule:

${b\left( {x,y} \right)} = {{128} - \frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}} + \frac{c_{2}^{(v)}}{2^{\frac{y}{d_{y}}}} - \frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}} + \frac{c_{2}^{(h)}}{2^{\frac{x}{d_{x}}}}}$

-   17. The video encoder of one of aspects 13 to 16, wherein the video    encoder is configured to filter the extended reference samples so as    to obtain filtered extended reference samples (r(x,−1−i), r(−1−i,y),    r(−1−i,−1−i) for i>0) (combined) using one of a 3-tap filter, a    5-tap filter and a 7-tap filter and to use the filtered extended    reference samples for the prediction.-   18. The video encoder of one of aspects 13 to 17, wherein the video    encoder is configured to use a combination of extended corner    reference samples of the prediction block and of extended reference    samples being arranged in a corner region of reference samples    (r(−1−i,−1−i)).-   19. The video encoder of aspect 18, wherein the video encoder is    configured to obtain the combined prediction based on the    determination rule:

$\mspace{79mu} {{p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}\frac{\sum_{x_{0} = {- 1}}^{{- 1} - i}{r\left( {x_{0},{{- 1} - i}} \right)}}{i + 1}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}\text{?}}}\end{matrix}}{128}}$ ?indicates text missing or illegible when filed

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and

$\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}$

for i>0 are the combined extended corner reference samples with respectto a boundary of the prediction block and b(x,y) denotes a normalizationfactor.

-   20. The video encoder of one of aspects 13 to 19, wherein the video    encoder is configured to obtain the prediction p(x,y) based on an    intra-picture prediction.-   21. The video encoder of aspect 20, wherein the video encoder is    configured to use only planar prediction as intra-picture    prediction.-   22. The video encoder of one of aspects 13 to 21, wherein the video    encoder is configured, for each encoded video block, to determine a    parameter set identifying the combination of the prediction and the    filtered extended reference samples.-   23. The video encoder of aspect 22, wherein the video encoder is    configured to determine the parameter set identifying the    combination of the prediction and the filtered extended reference    samples using a look-up table containing sets for different block    sizes of the prediction block.-   24. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set, the subset being associated        with the plurality of extended reference samples,    -   wherein the video encoder is configured to weightedly (w₀;        w_(i)) combine the first prediction (p₀(x,y)) and the second        prediction (p_(i)(x,y)) so as to obtain a combined prediction        (p(x,y)) as prediction for the prediction block in the coding        data.-   25. The video encoder of aspect 24, wherein the video encoder is    configured to use the first prediction and the second prediction    according to a predefined combination being a portion of possible    combinations of enabled first prediction modes and enabled second    prediction modes.-   26. The video encoder of aspect 24 or 25, wherein the video encoder    is configured to signal either the first prediction mode or the    second prediction mode whilst not signaling the other prediction    mode.-   27. The video encoder of one of aspects 24 to 26, wherein the video    encoder is configured to exclusively use a planar prediction mode as    one of the first prediction mode and the second prediction mode.-   28. The video encoder of one of aspects 24 to 27, wherein the video    encoder is configured to adapt a first weight applied to the first    prediction in the combined prediction and a second weight applied to    the second prediction in the combined prediction based on a block    size of the prediction block; and/or    -   adapt the first weight based on the first prediction mode or the        second weight based on the second prediction mode.-   29 The video encoder of one of aspects 24 to 28, wherein the video    encoder is configured to adapt a first weight applied to the first    prediction in the combined prediction and a second weight applied to    the second prediction in the combined prediction based on a    position.-   30. The video encoder of aspect 29, wherein the video encoder is    configured to adapt the first weight and the second weight based on    the determination rule

p(x,y)=w ₀(x,y)p ₀(x,y)w _(i)(x,y)p _(i)(x,y)

wherein w₀(x,y) is the first weight based on the position x,y in theprediction block, w_(i) is the second weight based on the position x,yin the prediction block, p₀(x,y) is the first prediction for theposition x,y and p_(i)(x,y) is the second prediction for the positionx,y, and i indicates the extended reference samples to be used for thesecond prediction.

-   31. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   signal a mode information (m) indicating the prediction mode        used for predicting the prediction block; and    -   afterwards signal a parameter information (i) indicating a        subset of the extended reference samples used for the prediction        mode if the prediction mode is contained in the second set of        prediction modes; and to skip signaling the parameter        information when the used prediction mode is not contained in        the second set of prediction modes.-   32. The video encoder of aspect 31, wherein the video encoder is    configured to skip signaling the parameter information, when the    mode information indicates a DC mode or a planar mode.-   33. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of reference samples comprising        nearest reference samples of the picture directly neighboring        the prediction block and a plurality of extended reference        samples, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   signal a parameter information (i) indicating a subset of the        plurality of reference samples used for the prediction mode, the        subset of the plurality of reference samples comprising nearest        reference samples only or extended reference samples;    -   afterwards signal a mode information (m) indicating the        prediction mode used for predicting the prediction block,        wherein the mode information indicates a prediction mode from a        subset of modes, the subset being restricted to a set of allowed        prediction modes according to the parameter information (i).-   34. The video encoder of one of aspects 31 to 33, wherein the    extended reference samples in modes contained in the second set of    prediction modes are used in addition to the nearest reference    samples.-   35. The video encoder of one of aspects 31 to 34, wherein the first    set of prediction modes describes prediction modes allowed for being    used with the nearest reference samples, wherein the second set of    prediction modes describes prediction modes of the first set of    prediction modes being also allowed for being used with the extended    reference samples.-   36. The video encoder of one of aspects 31 to 35, wherein a range of    values of the parameter information covers a use of the nearest    reference values only and a use of different subsets of extended    reference values.-   37. The video encoder of aspect 36, wherein different portions of    extended reference samples comprise a different distance to the    prediction block.-   38. The video encoder of aspect 36 or 37, wherein the video encoder    is configured to set the parameter information to one of a    predefined number of values, the value indicating a number and a    distance of reference samples used for the prediction mode.-   39. The video encoder of one of aspects 31 to 38, wherein the video    encoder is configured to determine the first set of prediction modes    and/or the second set of prediction modes based on a most probable    mode coding.-   40. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set being associated with the        plurality of extended reference samples,    -   wherein the video encoder is configured to combine the first        prediction and the second prediction so as to obtain a combined        prediction as prediction for the prediction block in the coding        data.-   41. The video encoder of aspect 40, wherein the prediction block is    a first prediction block, wherein the video encoder is configured to    predict a second prediction block of the video using a plurality of    nearest reference samples associated with the second prediction    block in absence of a plurality of extended reference samples    associated with the second prediction block;    -   wherein the video encoder is configured to signal a combining        information indicating that the prediction in the coding data is        based on a combination of predictions or is based on a        prediction using the plurality of extended reference samples in        absence of the plurality of nearest reference samples.-   42. The video encoder of aspect 40 or 41, wherein the video encoder    is configured to use the first prediction mode as a predefined    prediction mode.-   43. The video encoder of aspect 42, wherein the video encoder is    configured to select the first prediction mode as being a same mode    as the second prediction mode and using the nearest reference    samples in absence of the extended reference samples; or to use the    first prediction mode as preset prediction mode.-   44. Video encoder configured to:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;        and    -   use the plurality of extended reference samples according to a        predefined set of pluralities of extended reference samples.-   45. The video encoder of aspect 44, wherein the video encoder is    configured to determine the predefined set of pluralities of    extended reference samples such that pluralities in the set differ    with respect to each other by a number or combination of lines    and/or rows of samples of the picture to be used as reference    samples.-   46. The video encoder of aspect 45, wherein the video encoder is    configured to determine the predefined set of pluralities of    extended reference samples based on a block size of the prediction    block and/or a prediction mode used to predict the prediction block.-   47. The video encoder of aspect 45 or 46, wherein the video encoder    is configured to determine the set of pluralities of extended    reference samples for a block size of the prediction block being at    least a predefined threshold and to skip signaling the set of    pluralities of extended reference samples when the block size is    below the predefined threshold value or to skip signaling the set of    pluralities of extended reference samples based on a position of the    set of pluralities of extended reference samples within a coding    tree block.-   48. The video encoder of aspect 47, wherein the predefined threshold    is a predefined number of samples along a width or height of the    prediction block and/or a predefined aspect ratio of the prediction    block along the width and the height.-   49. The video encoder of aspect 48, wherein the predefined number of    samples is 8 and/or wherein the aspect ratio is greater than 1/4 and    less than 4.-   50. The video encoder of one of aspects 44 to 49, wherein the video    encoder is configured to predict the prediction block as a first    prediction block using the plurality of extended reference samples    and to predict a second prediction block not using extended    reference samples, wherein the video encoder is configured to signal    a predefined set of pluralities of extended reference samples    associated with the first prediction block and to not signal a    predefined set of extended reference samples in associated with the    second prediction block.-   51. The video encoder of one of aspects 44 to 50, wherein the video    encoder is configured to signal, for each prediction block,    information indicating one of a specific plurality of a set of    pluralities of extended reference samples and a use of nearest    reference samples only before information indicating the    intra-picture prediction mode.-   52. The video encoder of aspect 51, wherein the video encoder is    configured to signal the information indicating the intra-picture    prediction so as to thereby indicate prediction modes that are in    accordance with the indicated specific plurality of the set of    pluralities of extended reference samples or in accordance with the    indicated use of nearest reference samples, only.-   53. Video encoder configured to:    -   encode, by block based predictive encoding a plurality of        prediction blocks, pictures of a video into coding data, wherein        the block based predictive encoding comprises an intra-picture        prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of the plurality of prediction blocks, a plurality of        extended reference samples of the picture, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples, directly        neighboring the prediction block;    -   wherein the video encoder is configured to determine the        extended reference samples so as to be at least partially a part        of an adjacent prediction block of the plurality of prediction        blocks, and to determine that the adjacent prediction block has        not yet been predicted; and    -   to signal information indicating the extended prediction samples        associated to the prediction block and arranged in the adjacent        prediction block as unavailable samples.-   54. The video encoder of aspect 53, wherein the video encoder is    configured to encode the pictures by parallel encoding lines of    blocks according to a wavefront approach, and to predict the    prediction block based on an angular prediction, wherein the video    encoder is configured to determine the extended reference samples to    be used for predicting the prediction block so as to be arranged in    already predicted blocks of the picture.-   55. The video encoder of aspect 53 or 54, wherein the video encoder    is configured to signal the extended prediction samples associated    to the prediction block and arranged in the adjacent prediction    block variantly as unavailable samples or available samples on a    sequence level, a picture level or a slice level.-   56. The video encoder of one of aspects 53 to 55, wherein the video    encoder is configured to signal the information indicating the    extended prediction samples associated to the prediction block and    arranged in the adjacent prediction block as unavailable samples    together with information indicating a parallel coding of the    picture.-   57. The video encoder of one of previous aspects, wherein the video    encoder is configured to determine a list of most probable    prediction modes based on a use of the plurality of nearest    reference samples or the use of the plurality of extended reference    samples for the prediction mode, wherein the video encoder is    configured to substitute prediction modes restricted for the used    reference samples by modes allowed for the prediction mode.-   58. The video encoder of one of previous aspects, wherein the video    encoder is configured to apply prediction using extended reference    samples to pictures comprising luma information only.-   59. The video encoder of one of previous aspects, wherein the video    encoder is configured to generate extended reference samples    exceeding a width and/or a height of nearest reference samples along    a first and a second image direction by padding from a closest    extended reference sample.-   60. The video encoder of one of previous aspects, wherein the video    encoder is configured to predict the prediction using an angular    prediction mode using only a subset of angles from possible angles    of the angular prediction mode and to exclude unused angles from    signaling encoding information to a decoder.-   61. The video encoder of one of previous aspects, wherein the    extended reference samples are arranged in at least 2 lines and rows    in addition to nearest reference samples, advantageously at least 3    lines and rows.-   62. The video encoder of one of previous aspects, wherein the video    encoder is configured to use a specific plurality of a set of    pluralities of extended reference samples for predicting the    prediction block, wherein the video encoder is configured to select    the specific plurality from the set of pluralities so as to comprise    a lowest similarity of picture content when compared to a plurality    of nearest reference samples extended by the set.-   63. The video encoder of aspect 62, wherein the video encoder is    configured to signal a use of extended reference samples using a    flag.-   64. The video encoder of one of previous aspects, wherein the video    encoder is configured to selectively use the extended reference    samples or nearest reference samples only, wherein the video encoder    is configured to transform a residual obtained by predicting the    prediction block using a first transformation procedure so as to    obtain a first transformation result and to transform the first    transformation result using a second transformation procedure so as    to obtain a second transformation result when the extended reference    samples are unused for predicting the prediction block.-   65. The video encoder of aspect 64, wherein the video encoder is    configured to signal a use of the secondary transform; or to    implicitly signal a non-use of the secondary transform when    indicating a use of the extended reference samples and to not    include information relating to a result of a secondary transform in    the coding data.-   66. The video encoder of one of previous aspects, wherein the    prediction is a prediction for a residual signal to be used in    combination with a quantized signal so as to decode the picture.-   67. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   sequentially determine an availability or unavailability of each        of the plurality of extended reference samples;    -   substitute an extended reference sample being determined as        unavailable by a substitution sample; and    -   use the substitution sample for the intra-picture prediction.-   68. The video decoder of aspect 67, wherein the video decoder is    configured to:    -   determine the availability or unavailability sequentially        according to a sequence;    -   determine the substitution sample as a copy a last extended        reference sample being    -   determined as available in the sequence; and/or determine the        substitution sample as a copy a next extended reference sample        being    -   determined as available in the sequence.-   69. The video decoder of aspect 68, wherein the video decoder is    configured to:    -   determine the availability or unavailability sequentially        according to a sequence;    -   determine the substitution sample based on a combination of an        extended reference sample being determined as available and        being arranged in the sequence prior to the reference sample        being determined as unavailable and of an extended reference        sample being determined as available and being arranged in the        sequence after the reference sample being determined as        unavailable.-   70. The video decoder of one of aspects 67 to 69, wherein the video    decoder is configured to:    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine an availability or unavailability of each of the        plurality of extended reference samples;    -   receive information indicating that a portion of available        extended reference samples of the plurality of extended        reference samples is larger than or equal a predetermined        threshold and use of the plurality of extended reference        samples; and skip using the plurality of extended reference        samples in absence of the information.-   71. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   filtering at least a subset of the plurality of extended        reference samples using a bilateral filter so as to obtain a        plurality of filtered extended reference samples; and    -   use the plurality of filtered extended reference samples for the        intra-picture prediction.-   72. The video encoder of aspect 71, wherein the video decoder is    configured to filter the plurality of extended reference samples    using one of a 3-tap filter, a 5-tap filter and a 7-tap filter.-   73. The video decoder of aspect 72, wherein the 3-tap filter, a    5-tap filter and a 7-tap filter are configured as bilateral filters,    wherein the video decoder is configured to predict the prediction    block using an angular prediction mode, and to select to use one of    the 3-tap filter, the 5-tap filter and the 7-tap filter based on an    angle used for the angular prediction, the angle arranged between a    horizontal or a vertical direction of the angular prediction mode;    and/or wherein the video decoder is configured to select to use one    of the 3-tap filter, the 5-tap filter and the 7-tap filter based on    a block size of the prediction block.-   74. The video encoder of aspect 73, wherein the video decoder is    configured to select a filter with increasing taps for increasing    angles from to a horizontal direction or vertical direction towards    a diagonal.-   75. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block,        wherein a plurality of nearest reference samples is arranged        along a first picture direction of the prediction block and        along a second picture direction of the prediction block;    -   map at least a part of the nearest reference samples arranged        along the second direction to extended reference samples being        arranged along the first direction, such that the mapped        reference samples exceed an extension of the prediction block        along the first picture direction; and    -   use the mapped extended reference samples for the prediction.-   76. The video decoder of aspect 75, wherein the video decoder is    configured to map the portion of nearest reference samples according    to a prediction mode used for predicting the prediction block.-   77. The video decoder of aspect 76, wherein the video decoder is    configured to map the portion of nearest reference samples according    to a direction used in the prediction mode for predicting the    prediction block.-   78. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   wherein the video decoder is configured to boundary filtering in        a mode where no extended samples are used; and not to use        boundary filtering when extended samples are used; or wherein        the video decoder is configured to boundary filtering at least a        subset of the plurality of nearest reference samples and not        using boundary filtering for the extended samples.-   79. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   determining, in the intra-picture prediction, for decoding a        prediction block of a picture, a plurality of nearest reference        samples of the picture directly neighboring the prediction block        and a plurality of extended reference samples, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples;    -   determining a prediction for the prediction block using the        extended reference samples;    -   filtering the extended reference samples so as to obtain a        plurality of filtered extended reference samples; and    -   combining the prediction and the filtered extended reference        samples so as to obtain a combined prediction for the prediction        block.-   80. The video decoder of aspect 79, wherein the video decoder is    configured to combine the prediction and extended reference samples    being arranged in a major diagonal or minor diagonal of samples with    respect to the prediction block.-   81. The video decoder of aspect 79 or 80, wherein the video decoder    is configured to combine the prediction and the extended reference    samples based on the determination rule:

$\mspace{20mu} {{p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}}{r\left( {{{- 1} - i},{{- 1} - i}} \right)}} +}\end{matrix} \\{{b\left( {x,y} \right)} \cdot {p\left( \text{?} \right.}}\end{matrix}}{128}}$ ?indicates text missing or illegible when filed

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and r(−1−i,−1−i) for i>0 is an extended cornerreference sample of the plurality of extended reference samples withrespect to a boundary of the prediction block and b(x,y) denotes anormalization factor.

-   82. The video decoder of aspect 83, wherein the normalization factor    is determined based on the determination rule:

${b\left( {x,y} \right)} = {{128} - \frac{c_{1}^{(v)}}{2^{\lfloor\frac{y}{d_{y}}\rfloor}} + \frac{c_{2}^{(v)}}{2^{\frac{y}{d_{y}}}} - \frac{c_{1}^{(h)}}{2^{\lfloor\frac{x}{d_{x}}\rfloor}} + \frac{c_{2}^{(h)}}{2^{\frac{x}{d_{x}}}}}$

-   83. The video decoder of one of aspects 79 to 82, wherein the video    decoder is configured to filter the extended reference samples so as    to obtain filtered extended reference samples (r(x,−1−i), r(−1−i,y),    r(−1−i,−1−i) for i>0) (combined) using one of a 3-tap filter, a    5-tap filter and a 7-tap filter and to use the filtered extended    reference samples for the prediction.-   84. The video decoder of one of aspects 79 to 83, wherein the video    decoder is configured to use a combination of extended corner    reference samples of the prediction block and of extended reference    samples being arranged in a corner region of reference samples    (r(−1−i,−1−i)).-   85. The video decoder of aspect 84, wherein the video decoder is    configured to obtain the combined prediction based on the    determination rule:

$\mspace{20mu} {{p_{c}\left( {x,y} \right)} = \frac{\begin{matrix}{{\frac{c_{1}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}{r\left( {x,{{- 1} - i}} \right)}} - {\frac{c_{2}^{(v)}}{2^{\lfloor{y/d_{y}}\rfloor}}\frac{\sum_{x_{0} = {- 1}}^{{- 1} - i}{r\left( {x_{0},{{- 1} - i}} \right)}}{i + 1}} +} \\{{\frac{c_{1}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}{r\left( {{{- 1} - i},y} \right)}} - {\frac{c_{2}^{(h)}}{2^{\lfloor{x/d_{x}}\rfloor}}\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}\text{?}}}\end{matrix}}{128}}$ ?indicates text missing or illegible when filed

wherein p_(c)(x,y) denotes the combined prediction for coordinates x andy in the prediction block, p(x,y) denotes the prediction for coordinatesx and y in the prediction block, c₁ ^(v), c₂ ^(v), c₁ ^(h), c₂ ^(h) areprediction weights, d_(x) is a parameter set to 1 or 2 dependent on asize of the prediction block in dimension x, d_(y) is a parameter set to1 or 2 dependent on a size of the prediction block in dimension y,r(x,−1−i) for i>0 is the extended top reference sample at horizontalposition x, r(−1−i,y) for i>0 is the extended left reference sample atvertical position y and

$\frac{\sum_{y_{0} = {- 1}}^{{- 1} - i}{r\left( {{{- 1} - i},y_{0}} \right)}}{i + 1}$

for i>0 are the combined extended corner reference samples with respectto a boundary of the prediction block and b(x,y) denotes a normalizationfactor.

-   86. The video decoder of one of aspects 79 to 85, wherein the video    decoder is configured to obtain the prediction p(x,y) based on an    intra-picture prediction.-   87. The video decoder of aspect 86, wherein the video decoder is    configured to use only planar prediction as intra-picture    prediction.-   88. The video decoder of one of aspects 79 to 87, wherein the video    decoder is configured, for each decoded video block, to determine a    parameter set identifying the combination of the prediction and the    filtered extended reference samples.-   89. The video decoder of aspect 88, wherein the video decoder is    configured to determine the parameter set identifying the    combination of the prediction and the filtered extended reference    samples using a look-up table containing sets for different block    sizes of the prediction block.-   90. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set, the subset being associated        with the plurality of extended reference samples,    -   wherein the video decoder is configured to weightedly (w₀;        w_(i)) combine the first prediction (p₀(x,y)) and the second        prediction (p₀(x,y)) so as to obtain a combined prediction        (p(x,y)) as prediction for the prediction block in the coding        data.-   91. The video decoder of aspect 90, wherein the video decoder is    configured to use the first prediction and the second prediction    according to a predefined combination being a portion of possible    combinations of enabled first prediction modes and enabled second    prediction modes.-   92. The video decoder of aspect 90 or 91, wherein the video decoder    is configured to receive a signal indicating the second prediction    mode whilst not receiving a signal indicating the first prediction    mode and to derive the first prediction mode from the second    prediction mode or a parameter information (i).-   93. The video decoder of one of aspects 90 to 92, wherein the video    decoder is configured to exclusively use a planar prediction mode as    one of the first prediction mode and the second prediction mode.-   94. The video decoder of one of aspects 90 to 93, wherein the video    decoder is configured to adapt a first weight applied to the first    prediction in the combined prediction and a second weight applied to    the second prediction in the combined prediction based on a block    size of the prediction block; and/or adapt the first weight based on    the first prediction mode or the second weight based on the second    prediction mode.    -   The video decoder of one of aspects 90 to 94, wherein the video        decoder is configured to adapt a first weight applied to the        first prediction in the combined prediction and a second weight        applied to the second prediction in the combined prediction        based on a position in the prediction block.-   96. The video decoder of aspect 95, wherein the video decoder is    configured to adapt the first weight and the second weight based on    the determination rule

p(x,y)=w ₀(x,y)p ₀(x,y)+w _(i)(x,y)p _(i)(x,y)

wherein w₀(x,y) is the first weight based on the position x,y in theprediction block, w_(i) is the second weight based on the position x,yin the prediction block, p₀(x,y) is the first prediction for theposition x,y and p_(i)(x,y) is the second prediction for the positionx,y, and i indicates the extended reference samples to be used for thesecond prediction.

-   97. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   receive a mode information (m) indicating the prediction mode        used for predicting the prediction block; and    -   afterwards receive a parameter information (i) indicating a        subset of the extended reference samples used for the prediction        mode thereby indicating that the prediction mode is contained in        the second set of prediction modes; and to determine that the        used prediction mode is not contained in the second set of        prediction modes when not receiving the parameter information        and to determine a use of the nearest reference samples for the        prediction.-   98. The video decoder of aspect 97, wherein the video decoder is    configured to determine the mode information as indicating a use of    a DC mode or a planar mode when not receiving the parameter    information.-   99. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of reference samples comprising        nearest reference samples of the picture directly neighboring        the prediction block and a plurality of extended reference        samples, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   receive a parameter information (i) indicating a subset of the        plurality of reference samples used for the prediction mode, the        subset of the plurality of reference samples comprising nearest        reference samples only or at least one extended reference        sample;    -   afterwards receive a mode information (m) indicating the        prediction mode used for predicting the prediction block,        wherein the mode information indicates a prediction mode from a        subset of modes, the subset being restricted to a set of allowed        prediction modes according to the parameter information (i).-   100. The video decoder of aspect 97 to 99, wherein the extended    reference samples in modes contained in the second set of prediction    modes are used in addition to the nearest reference samples.-   101. The video decoder of one of aspects 97 to 100, wherein the    first set of prediction modes describes prediction modes allowed for    being used with the nearest reference samples, wherein the second    set of prediction modes describes prediction modes of the first set    of prediction modes being also allowed for being used with the    extended reference samples.-   102. The video decoder of one of aspects 97 to 101, wherein a range    of values of the parameter information covers a use of the nearest    reference values only and a use of different subsets of extended    reference values.-   103. The video decoder of aspect 102, wherein different portions of    extended reference samples comprise a different distance to the    prediction block.-   104. The video decoder of aspect 102 or 103, wherein the video    decoder is configured to set the parameter information to one of a    predefined number of values, the value indicating a number and a    distance of reference samples used for the prediction mode.-   105. The video decoder of one of aspects 97 to 104, wherein the    video decoder is configured to determine the first set of prediction    modes and/or the second set of prediction modes based on a most    probable mode coding.-   106. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set being associated with the        plurality of extended reference samples, wherein the video        decoder is configured to combine the first prediction and the        second prediction so as to obtain a combined prediction as        prediction for the prediction block in the coding data.-   107. The video decoder of aspect 106, wherein the prediction block    is a first prediction block, wherein the video decoder is configured    to predict a second prediction block of the video using a plurality    of nearest reference samples associated with the second prediction    block in absence of a plurality of extended reference samples    associated with the second prediction block;    -   wherein the video decoder is configured to receive a combining        information indicating that the prediction in the coding data is        based on a combination of predictions or is based on a        prediction using the plurality of extended reference samples in        absence of the plurality of nearest reference samples and do        decode the coding data accordingly.-   108. The video decoder of aspect 106 or 107, wherein the video    decoder is configured to use the first prediction mode as a    predefined prediction mode.-   109. The video decoder of aspect 108, wherein the video decoder is    configured to select the first prediction mode as being a same mode    as the second prediction mode and using the nearest reference    samples in absence of the extended reference samples; or to use the    first prediction mode as preset prediction mode.-   110. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;        and    -   use the plurality of extended reference samples according to a        predefined set of pluralities of extended reference samples.-   111. The video decoder of aspect 110, wherein the video decoder is    configured to determine the predefined set of pluralities of    extended reference samples such that pluralities in the set differ    with respect to each other by a number or combination of lines    and/or rows of samples of the picture to be used as reference    samples.-   112. The video decoder of aspect 111, wherein the video decoder is    configured to determine the predefined set of pluralities of    extended reference samples based on a block size of the prediction    block and/or a prediction mode used to predict the prediction block.-   113. The video decoder of aspect 111 or 112, wherein the video    decoder is configured to determine the set of pluralities of    extended reference samples for a block size of the prediction block    being at least a predefined threshold and to skip using the set of    pluralities of extended reference samples when the block size is    below the predefined threshold value.-   114. The video decoder of aspect 113, wherein the predefined    threshold is a predefined number of samples along a width or height    of the prediction block and/or a predefined aspect ratio of the    prediction block along the width and the height.-   115. The video decoder of aspect 114, wherein the predefined number    of samples is 8 and/or wherein the aspect ratio is greater than 1/4    and at less than 4.-   116. The video decoder of one of aspects 110 to 115, wherein the    video decoder is configured to predict the prediction block as a    first prediction block using the plurality of extended reference    samples and to predict a second prediction block not using extended    reference samples, wherein the video decoder is configured to    receive information indicating a predefined set of pluralities of    extended reference samples associated with the first prediction    block and to determine a predefined set of extended reference    samples in associated with the second prediction block in absence of    a respective signal.-   117. The video decoder of one of aspects 110 to 116, wherein the    video decoder is configured to receive, for each prediction block,    information indicating a one of a specific plurality of a set of    pluralities of extended reference samples and a use of nearest    reference samples only before information indicating the    intra-picture prediction mode.-   118. The video decoder of aspect 117, wherein the video decoder is    configured to receive the information indicating the intra-picture    prediction so as to thereby indicate prediction modes that are in    accordance with the indicated specific plurality of the set of    pluralities of extended reference samples or in accordance with the    indicated use of nearest reference samples, only.-   119. Video decoder configured to:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein for each picture a plurality        of prediction blocks is decoded, wherein the block based        predictive decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of the plurality of prediction blocks, a plurality of        extended reference samples of the picture, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples, directly        neighboring the prediction block;    -   wherein the video decoder is configured to determine the        extended reference samples so as to be at least partially a part        of an adjacent prediction block of the plurality of prediction        blocks, and to determine that the adjacent prediction block has        not yet been predicted; and to receive information indicating        the extended prediction samples associated to the prediction        block and arranged in the adjacent prediction block as        unavailable samples.-   120. The video decoder of aspect 119, wherein the video decoder is    configured to decode the pictures by parallel decoding lines of    blocks according to a wavefront approach, and to predict the    prediction block based on an angular prediction, wherein the video    decoder is configured to determine the extended reference samples to    be used for predicting the prediction block so as to be arranged in    already predicted blocks of the picture.-   121. The video decoder of aspect 119 or 120, wherein the video    decoder is configured to receive information indicating the extended    prediction samples associated to the prediction block and arranged    in the adjacent prediction block variantly as unavailable samples or    available samples on a sequence level, a picture level or a slice    level.-   122. The video decoder of one of aspects 119 to 121, wherein the    video decoder is configured to receive the information indicating    the extended prediction samples associated to the prediction block    and arranged in the adjacent prediction block as unavailable samples    together with information indicating a parallel decoding of the    picture.-   123. The video decoder of one of aspects 68 to 122, wherein the    video decoder is configured to determine a list of most probable    prediction modes based on a use of the plurality of nearest    reference samples or the use of the plurality of extended reference    samples for the prediction mode, wherein the video decoder is    configured to substitute prediction modes restricted for the used    reference samples by modes allowed for the prediction mode.-   124. The video decoder of one of aspects 68 to 123, wherein the    video decoder is configured to apply prediction using extended    reference samples to pictures comprising luma information only.-   125. The video decoder of one of aspects 68 to 124, wherein the    video decoder is configured to generate extended reference samples    exceeding a width and/or a height of nearest reference samples along    a first and a second image direction by padding from a closest    extended reference sample.-   126. The video decoder of one of aspects 68 to 125, wherein the    video decoder is configured to predict the prediction using an    angular prediction mode using only a subset of angles from possible    angles of the angular prediction mode and to exclude unused angles    from the prediction.-   127. The video decoder of one of aspects 68 to 126, wherein the    extended reference samples are arranged in at least 2 lines and rows    in addition to nearest reference samples, advantageously at least 3    lines and rows.-   128. The video decoder of one of aspects 68 to 127, wherein the    video decoder is configured to use a specific plurality of a set of    pluralities of extended reference samples for predicting the    prediction block, wherein the video decoder is configured to select    the specific plurality from the set of pluralities so as to comprise    a lowest similarity of picture content when compared to a plurality    of nearest reference samples extended by the set.-   129. The video decoder of aspect 128, wherein the video decoder is    configured to receive information indicating a use of extended    reference samples by a flag.-   130. The video decoder of one of aspects 68 to 129, wherein the    video decoder is configured to selectively use the extended    reference samples or nearest reference samples only, wherein the    video decoder is configured to transform a residual obtained by    predicting the prediction block using a first transformation    procedure so as to obtain a first transformation result and to    transform the first transformation result using a second    transformation procedure so as to obtain a second transformation    result when the extended reference samples are unused for predicting    the prediction block.-   131. The video decoder of aspect 130, wherein the video decoder is    configured to receive information indicating a use of the secondary    transform; or to derive a non-use of the secondary transform when    indicating a use of the extended reference samples and to not    receive information relating to a result of a secondary transform in    the coding data.-   132. The video decoder of one of aspects 68 to 131, wherein the    prediction is a prediction for a residual signal to be used in    combination with a quantized signal so as to decode the picture.-   133. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   sequentially determine an availability or unavailability of each        of the plurality of extended reference samples;    -   substitute an extended reference sample being determined as        unavailable by a substitution sample; and    -   use the substitution sample for the intra-picture prediction.-   134. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   filtering at least a subset of the plurality of extended        reference samples using a bilateral filter so as to obtain a        plurality of filtered extended reference samples; and    -   use the plurality of filtered extended reference samples for the        intra-picture prediction.-   135. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block,        wherein a plurality of nearest reference samples is arranged        along a first picture direction of the prediction block and        along a second picture direction of the prediction block;    -   map at least a part of the nearest reference samples arranged        along the second direction to extended reference samples being        arranged along the first direction, such that the mapped        reference samples exceed an extension of the prediction block        along the first picture direction; and use the mapped extended        reference samples for the prediction.-   136. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   boundary filtering in a mode where no extended samples are used;        and not to use boundary filtering when extended samples are        used; or boundary filtering at least a subset of the plurality        of nearest reference samples and not using boundary filtering        for the extended samples.-   137. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   determining, in the intra-picture prediction, for encoding a        prediction block of a picture, a plurality of nearest reference        samples of the picture directly neighboring the prediction block        and a plurality of extended reference samples, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples;    -   determining a prediction for the prediction block using the        extended reference samples;    -   filtering the extended reference samples so as to obtain a        plurality of filtered extended reference samples; and    -   combining the prediction and the filtered extended reference        samples so as to obtain a combined prediction for the prediction        block.-   138. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set, the subset being associated        with the plurality of extended reference samples,    -   to weightedly (w₀; w_(i)) combine the first prediction (p₀(x,y))        and the second prediction (p_(i)(x,y)) so as to obtain a        combined prediction (p(x,y)) as prediction for the prediction        block in the coding data.-   139. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   signal a mode information (m) indicating the prediction mode        used for predicting the prediction block; and    -   afterwards signal a parameter information (i) indicating a        subset of the extended reference samples used for the prediction        mode if the prediction mode is contained in the second set of        prediction modes; and to skip signaling the parameter        information when the used prediction mode is not contained in        the second set of prediction modes.-   140. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of reference samples comprising        nearest reference samples of the picture directly neighboring        the prediction block and a plurality of extended reference        samples, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   signal a parameter information (i) indicating a subset of the        plurality of reference samples used for the prediction mode, the        subset of the plurality of reference samples comprising nearest        reference samples only or extended reference samples;    -   afterwards signal a mode information (m) indicating the        prediction mode used for predicting the prediction block,        wherein the mode information indicates a prediction mode from a        subset of modes, the subset being restricted to a set of allowed        prediction modes according to the parameter information (i).-   141. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set being associated with the        plurality of extended reference samples,    -   combine the first prediction and the second prediction so as to        obtain a combined prediction as prediction for the prediction        block in the coding data.-   142. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding, pictures of a video        into coding data, wherein the block based predictive encoding        comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;        and use the plurality of extended reference samples according to        a predefined set of pluralities of extended reference samples.-   143. Method for encoding a video, the method comprising:    -   encode, by block based predictive encoding a plurality of        prediction blocks, pictures of a video into coding data, wherein        the block based predictive encoding comprises an intra-picture        prediction;    -   use, for the intra-picture prediction, for encoding a prediction        block of the plurality of prediction blocks, a plurality of        extended reference samples of the picture, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples, directly        neighboring the prediction block;    -   determine the extended reference samples so as to be at least        partially a part of an adjacent prediction block of the        plurality of prediction blocks, and to determine that the        adjacent prediction block has not yet been predicted; and    -   to signal information indicating the extended prediction samples        associated to the prediction block and arranged in the adjacent        prediction block as unavailable samples.-   144. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for encoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   sequentially determine an availability or unavailability of each        of the plurality of extended reference samples;    -   substitute an extended reference sample being determined as        unavailable by a substitution sample; and    -   use the substitution sample for the intra-picture prediction.-   145. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;    -   filtering at least a subset of the plurality of extended        reference samples using a bilateral filter so as to obtain a        plurality of filtered extended reference samples; and use the        plurality of filtered extended reference samples for the        intra-picture prediction.-   146. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block,        wherein a plurality of nearest reference samples is arranged        along a first picture direction of the prediction block and        along a second picture direction of the prediction block;    -   map at least a part of the nearest reference samples arranged        along the second direction to extended reference samples being        arranged along the first direction, such that the mapped        reference samples exceed an extension of the prediction block        along the first picture direction; and use the mapped extended        reference samples for the prediction.-   147. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   boundary filtering in a mode where no extended samples are used;        and not to use boundary filtering when extended samples are        used; or boundary filtering at least a subset of the plurality        of nearest reference samples and not using boundary filtering        for the extended samples.-   148. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   determining, in the intra-picture prediction, for decoding a        prediction block of a picture, a plurality of nearest reference        samples of the picture directly neighboring the prediction block        and a plurality of extended reference samples, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples;    -   determining a prediction for the prediction block using the        extended reference samples; and    -   filtering the extended reference samples so as to obtain a        plurality of filtered extended reference samples; and    -   combining the prediction and the filtered extended reference        samples so as to obtain a combined prediction for the prediction        block.-   149. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set, the subset being associated        with the plurality of extended reference samples,    -   weightedly (w₀; w_(i)) combine the first prediction (p₀(x,y))        and the second prediction (p_(i)(x,y)) so as to obtain a        combined prediction (p(x,y)) as prediction for the prediction        block in the coding data.-   150. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   receive a mode information (m) indicating the prediction mode        used for predicting the prediction block; and    -   afterwards receive a parameter information (i) indicating a        subset of the extended reference samples used for the prediction        mode thereby indicating that the prediction mode is contained in        the second set of prediction modes; and determine that the used        prediction mode is not contained in the second set of prediction        modes when not receiving the parameter information and to        determine a use of the nearest reference samples for the        prediction.-   151. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of reference samples comprising        nearest reference samples of the picture directly neighboring        the prediction block and a plurality of extended reference        samples, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples;    -   use a prediction mode being one of a first set of prediction        modes for predicting the prediction block using the nearest        reference samples; or being one of a second set of prediction        modes for predicting the prediction block using the extended        reference samples; wherein the second set of prediction modes is        a subset of the first set of prediction modes;    -   receive a parameter information (i) indicating a subset of the        plurality of reference samples used for the prediction mode, the        subset of the plurality of reference samples comprising nearest        reference samples only or at least one extended reference        samples;    -   afterwards receive a mode information (m) indicating the        prediction mode used for predicting the prediction block,        wherein the mode information indicates a prediction mode from a        subset of modes, the subset being restricted to a set of allowed        prediction modes according to the parameter information (i).-   152. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of nearest reference samples of        the picture directly neighboring the prediction block and/or a        plurality of extended reference samples, each extended reference        sample of the plurality of extended reference samples separated        from the prediction block at least by one nearest reference        sample of the plurality of reference samples;    -   determine a first prediction for the prediction block using a        first prediction mode of a set of prediction modes, the first        set of prediction modes comprising prediction modes using the        plurality of nearest reference samples in absence of the        extended reference samples;    -   determining a second prediction for the prediction block using a        second prediction mode of a second set of prediction modes, the        second set of prediction modes comprising a subset of the        prediction modes of the first set being associated with the        plurality of extended reference samples, combine the first        prediction and the second prediction so as to obtain a combined        prediction as prediction for the prediction block in the coding        data.-   153. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein the block based predictive        decoding comprises an intra-picture prediction;    -   use, in the intra-picture prediction, for decoding a prediction        block of a picture, a plurality of extended reference samples of        the picture, each extended reference sample of the plurality of        extended reference samples separated from the prediction block        at least by one nearest reference sample of the plurality of        reference samples, directly neighboring the prediction block;        and    -   use the plurality of extended reference samples according to a        predefined set of pluralities of extended reference samples.-   154. Method for decoding a video, the method comprising:    -   decode, by block based predictive decoding, pictures coded in        coding data into a video, wherein for each picture a plurality        of prediction blocks is decoded, wherein the block based        predictive decoding comprises an intra-picture prediction;    -   use, for the intra-picture prediction, for decoding a prediction        block of the plurality of prediction blocks, a plurality of        extended reference samples of the picture, each extended        reference sample of the plurality of extended reference samples        separated from the prediction block at least by one nearest        reference sample of the plurality of reference samples, directly        neighboring the prediction block;    -   determine the extended reference samples so as to be at least        partially a part of an adjacent prediction block of the        plurality of prediction blocks, and to determine that the        adjacent prediction block has not yet been predicted; and        receive information indicating the extended prediction samples        associated to the prediction block and arranged in the adjacent        prediction block as unavailable samples.-   155. Non-transitory storage medium having stored thereon a computer    program having a program code for performing, when running on a    computer, a method according to one of aspects 133-154.

Although some aspects have been described in the context of anapparatus, it is clear that these aspects also represent a descriptionof the corresponding method, where a block or device corresponds to amethod step or a feature of a method step. Analogously, aspectsdescribed in the context of a method step also represent a descriptionof a corresponding block or item or feature of a correspondingapparatus.

Depending on certain implementation requirements, embodiments of theinvention can be implemented in hardware or in software. Theimplementation can be performed using a digital storage medium, forexample a floppy disk, a DVD, a CD, a ROM, a PROM, an EPROM, an EEPROMor a FLASH memory, having electronically readable control signals storedthereon, which cooperate (or are capable of cooperating) with aprogrammable computer system such that the respective method isperformed.

Some embodiments according to the invention comprise a data carrierhaving electronically readable control signals, which are capable ofcooperating with a programmable computer system, such that one of themethods described herein is performed.

Generally, embodiments of the present invention can be implemented as acomputer program product with a program code, the program code beingoperative for performing one of the methods when the computer programproduct runs on a computer. The program code may for example be storedon a machine-readable carrier.

Other embodiments comprise the computer program for performing one ofthe methods described herein, stored on a machine-readable carrier.

In other words, an embodiment of the inventive method is, therefore, acomputer program having a program code for performing one of the methodsdescribed herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a datacarrier (or a digital storage medium, or a computer-readable medium)comprising, recorded thereon, the computer program for performing one ofthe methods described herein.

A further embodiment of the inventive method is, therefore, a datastream or a sequence of signals representing the computer program forperforming one of the methods described herein. The data stream or thesequence of signals may for example be configured to be transferred viaa data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example acomputer, or a programmable logic device, configured to or adapted toperform one of the methods described herein.

A further embodiment comprises a computer having installed thereon thecomputer program for performing one of the methods described herein.

In some embodiments, a programmable logic device (for example a fieldprogrammable gate array) may be used to perform some or all of thefunctionalities of the methods described herein. In some embodiments, afield programmable gate array may cooperate with a microprocessor inorder to perform one of the methods described herein. Generally, themethods are performed by any hardware apparatus.

While this invention has been described in terms of several advantageousembodiments, there are alterations, permutations, and equivalents whichfall within the scope of this invention. It should also be noted thatthere are many alternative ways of implementing the methods andcompositions of the present invention. It is therefore intended that thefollowing appended claims be interpreted as including all suchalterations, permutations, and equivalents as fall within the truespirit and scope of the present invention.

1. Video decoder configured to: decode, by block based predictive decoding, pictures coded in coding data into a video, wherein the block based predictive decoding comprises an intra-picture prediction; use, in the intra-picture prediction, for encoding a prediction block of a picture, a plurality of extended reference samples of the picture, each extended reference sample of the plurality of extended reference samples separated from the prediction block at least by one nearest reference sample of the plurality of reference samples, directly neighboring the prediction block; sequentially determine an availability or unavailability of each of the plurality of extended reference samples; substitute an extended reference sample being determined as unavailable by a substitution sample; and use the substitution sample for the intra-picture prediction.
 2. The video decoder of claim 1, wherein the video decoder is configured to: determine the availability or unavailability sequentially according to a sequence; determine the substitution sample as a copy a last extended reference sample being determined as available in the sequence; and/or determine the substitution sample as a copy a next extended reference sample being determined as available in the sequence.
 3. The video decoder of claim 2, wherein the video decoder is configured to: determine the availability or unavailability sequentially according to a sequence; determine the substitution sample based on a combination of an extended reference sample being determined as available and being arranged in the sequence prior to the reference sample being determined as unavailable and of an extended reference sample being determined as available and being arranged in the sequence after the reference sample being determined as unavailable.
 4. Video decoder configured to: decode, by block based predictive decoding, pictures coded in coding data into a video, wherein the block based predictive decoding comprises an intra-picture prediction; use, for the intra-picture prediction, for decoding a prediction block of a picture, a plurality of nearest reference samples of the picture directly neighboring the prediction block and a plurality of extended reference samples, each extended reference sample of the plurality of extended reference samples separated from the prediction block at least by one nearest reference sample of the plurality of reference samples; wherein the video decoder is configured to boundary filtering in a mode where no extended samples are used; and not to use boundary filtering when extended samples are used; or wherein the video decoder is configured to boundary filtering at least a subset of the plurality of nearest reference samples and not using boundary filtering for the extended samples.
 5. Video decoder configured to: decode, by block based predictive decoding, pictures coded in coding data into a video, wherein the block based predictive decoding comprises an intra-picture prediction; use, for the intra-picture prediction, for decoding a prediction block of a picture, a plurality of nearest reference samples of the picture directly neighboring the prediction block and/or a plurality of extended reference samples, each extended reference sample of the plurality of extended reference samples separated from the prediction block at least by one nearest reference sample of the plurality of reference samples; use a prediction mode being one of a first set of prediction modes for predicting the prediction block using the nearest reference samples; or being one of a second set of prediction modes for predicting the prediction block using the extended reference samples; wherein the second set of prediction modes is a subset of the first set of prediction modes; receive a mode information indicating the prediction mode used for predicting the prediction block; and afterwards receive a parameter information indicating a subset of the extended reference samples used for the prediction mode thereby indicating that the prediction mode is comprised in the second set of prediction modes; and to determine that the used prediction mode is not comprised in the second set of prediction modes when not receiving the parameter information and to determine a use of the nearest reference samples for the prediction.
 6. The video decoder of claim 5, wherein the video decoder is configured to determine the mode information as indicating a use of a DC mode or a planar mode when not receiving the parameter information.
 7. Video decoder configured to: decode, by block based predictive decoding, pictures coded in coding data into a video, wherein the block based predictive decoding comprises an intra-picture prediction; use, for the intra-picture prediction, for decoding a prediction block of a picture, a plurality of reference samples comprising nearest reference samples of the picture directly neighboring the prediction block and a plurality of extended reference samples, each extended reference sample of the plurality of extended reference samples separated from the prediction block at least by one nearest reference sample of the plurality of reference samples; use a prediction mode being one of a first set of prediction modes for predicting the prediction block using the nearest reference samples; or being one of a second set of prediction modes for predicting the prediction block using the extended reference samples; wherein the second set of prediction modes is a subset of the first set of prediction modes; receive a parameter information indicating a subset of the plurality of reference samples used for the prediction mode, the subset of the plurality of reference samples comprising nearest reference samples only or at least one extended reference sample; afterwards receive a mode information indicating the prediction mode used for predicting the prediction block, wherein the mode information indicates a prediction mode from a subset of modes, the subset being restricted to a set of allowed prediction modes according to the parameter information.
 8. The video decoder of claim 7, wherein the extended reference samples in modes comprised in the second set of prediction modes are used in addition to the nearest reference samples.
 9. The video decoder of claim 5, wherein the first set of prediction modes describes prediction modes allowed for being used with the nearest reference samples, wherein the second set of prediction modes describes prediction modes of the first set of prediction modes being also allowed for being used with the extended reference samples.
 10. The video decoder of claim 5, wherein a range of values of the parameter information covers a use of the nearest reference values only and a use of different subsets of extended reference values.
 11. The video decoder of claim 10, wherein different portions of extended reference samples comprise a different distance to the prediction block.
 12. The video decoder of claim 10, wherein the video decoder is configured to set the parameter information to one of a predefined number of values, the value indicating a number and a distance of reference samples used for the prediction mode.
 13. The video decoder of claim 5, wherein the video decoder is configured to determine the first set of prediction modes and/or the second set of prediction modes based on a most probable mode coding.
 14. Video decoder configured to: decode, by block based predictive decoding, pictures coded in coding data into a video, wherein the block based predictive decoding comprises an intra-picture prediction; use, in the intra-picture prediction, for decoding a prediction block of a picture, a plurality of extended reference samples of the picture, each extended reference sample of the plurality of extended reference samples separated from the prediction block at least by one nearest reference sample of the plurality of reference samples, directly neighboring the prediction block; and use the plurality of extended reference samples according to a predefined set of pluralities of extended reference samples.
 15. The video decoder of claim 14, wherein the video decoder is configured to determine the predefined set of pluralities of extended reference samples such that pluralities in the set differ with respect to each other by a number or combination of lines and/or rows of samples of the picture to be used as reference samples.
 16. The video decoder of claim 15, wherein the video decoder is configured to determine the predefined set of pluralities of extended reference samples based on a block size of the prediction block and/or a prediction mode used to predict the prediction block.
 17. The video decoder of claim 15, wherein the video decoder is configured to determine the set of pluralities of extended reference samples for a block size of the prediction block being at least a predefined threshold and to skip using the set of pluralities of extended reference samples when the block size is below the predefined threshold value.
 18. The video decoder of claim 17, wherein the predefined threshold is a predefined number of samples along a width or height of the prediction block and/or a predefined aspect ratio of the prediction block along the width and the height.
 19. The video decoder of claim 18, wherein the predefined number of samples is 8 and/or wherein the aspect ratio is greater than 1/4 and at less than
 4. 20. The video decoder of claim 14, wherein the video decoder is configured to predict the prediction block as a first prediction block using the plurality of extended reference samples and to predict a second prediction block not using extended reference samples, wherein the video decoder is configured to receive information indicating a predefined set of pluralities of extended reference samples associated with the first prediction block and to determine a predefined set of extended reference samples in associated with the second prediction block in absence of a respective signal.
 21. The video decoder of claim 14, wherein the video decoder is configured to receive, for each prediction block, information indicating a one of a specific plurality of a set of pluralities of extended reference samples and a use of nearest reference samples only before information indicating the intra-picture prediction mode.
 22. The video decoder of claim 21, wherein the video decoder is configured to receive the information indicating the intra-picture prediction so as to thereby indicate prediction modes that are in accordance with the indicated specific plurality of the set of pluralities of extended reference samples or in accordance with the indicated use of nearest reference samples, only.
 23. Video decoder configured to: decode, by block based predictive decoding, pictures coded in coding data into a video, wherein for each picture a plurality of prediction blocks is decoded, wherein the block based predictive decoding comprises an intra-picture prediction; use, for the intra-picture prediction, for decoding a prediction block of the plurality of prediction blocks, a plurality of extended reference samples of the picture, each extended reference sample of the plurality of extended reference samples separated from the prediction block at least by one nearest reference sample of the plurality of reference samples, directly neighboring the prediction block; wherein the video decoder is configured to determine the extended reference samples so as to be at least partially a part of an adjacent prediction block of the plurality of prediction blocks, and to determine that the adjacent prediction block has not yet been predicted; and to receive information indicating the extended prediction samples associated to the prediction block and arranged in the adjacent prediction block as unavailable samples.
 24. The video decoder of claim 23, wherein the video decoder is configured to decode the pictures by parallel decoding lines of blocks according to a wavefront approach, and to predict the prediction block based on an angular prediction, wherein the video decoder is configured to determine the extended reference samples to be used for predicting the prediction block so as to be arranged in already predicted blocks of the picture.
 25. The video decoder of claim 23, wherein the video decoder is configured to receive information indicating the extended prediction samples associated to the prediction block and arranged in the adjacent prediction block variantly as unavailable samples or available samples on a sequence level, a picture level or a slice level.
 26. The video decoder of claim 23, wherein the video decoder is configured to receive the information indicating the extended prediction samples associated to the prediction block and arranged in the adjacent prediction block as unavailable samples together with information indicating a parallel decoding of the picture.
 27. The video decoder of claim 1, wherein the video decoder is configured to determine a list of most probable prediction modes based on a use of the plurality of nearest reference samples or the use of the plurality of extended reference samples for the prediction mode, wherein the video decoder is configured to substitute prediction modes restricted for the used reference samples by modes allowed for the prediction mode.
 28. The video decoder of claim 1, wherein the video decoder is configured to apply prediction using extended reference samples to pictures comprising luma information only.
 29. The video decoder of claim 1, wherein the video decoder is configured to generate extended reference samples exceeding a width and/or a height of nearest reference samples along a first and a second image direction by padding from a closest extended reference sample.
 30. The video decoder of claim 1, wherein the video decoder is configured to predict the prediction using an angular prediction mode using only a subset of angles from possible angles of the angular prediction mode and to exclude unused angles from the prediction.
 31. The video decoder of claim 1, wherein the extended reference samples are arranged in at least 2 lines and rows in addition to nearest reference samples, advantageously at least 3 lines and rows.
 32. The video decoder of claim 1, wherein the prediction is a prediction for a residual signal to be used in combination with a quantized signal so as to decode the picture. 